From Boosted Tech
The 5.0 Windsor in standard form is quite underpowered, although the amount of parts available from the aftermarket is staggering, due to the fact the 5.0 used in E-Series/AU Falcons is virtually the same engine as the 86-95 Ford Mustang.
If you're new to modifying a 5.0, your first stop should be here,  SummitRacing.com, a US speed shop that has a massive amount of stock from all major manufacturers, is very well priced, does international shipping, and now offers instant automated quotes for international shipping. They also have additional information regarding extra parts needed and applications. It's now possible to build a complete engine from scratch from Summit.
Starting with the air intake, the factory MAF (Mass Air Flow) Sensor is quite restrictive, with an ID (Inside Diameter) of 55mm. On a standard engine this does the job, although it isn't ideal.
There are many options for upgrading the MAF, the most common option is to fit an AU Falcon V8 70mm MAF housing with the E-Series sensor, due to the AU sensor having a different plug. These bolt straight on, look like a factory part (funny about that..) and are not too hard to find for sale.
Other options from Ford are the US 'Cobra' 70mm MAF, which was fitted to the Mustang Cobra, EB GT, ED XR8 Sprint, EL GT and the NL Fairlane By Tickford. There is some debate on whether these items are suited for the standard injectors.
A popular aftermarket MAF is the Pro-M, which come in various sizes and mounting styles.
The standard 58mm TB is large enough for the job, although an upgrade will be required when modifications continue.
The most common option is the 65mm unit found on AU V8's.
The standard HO manifold is one of the biggest restrictions on the 5.0.
Again, the most popular option is to use the 'Explorer' (due to it being fitted to the late 90's Ford Explorer) manifold which features much larger staggered ports. One thing to be wary of is that the AU manifold doesn't have a provision for the ICT/IAT (Intake Charge Temp/Intake Air Temp respectively) sensor, which is usually drilled into the #5 runner on the lower manifold in E-Series. A common way around this is to mount the IAT sensor into the intake pipe, before the TB. The problem is that the ECU will be reading cooler intake temperatures, and run richer to compensate. While AU's use the IAT in this position, E-Series ECU's are not calibrated for the temperature change. As of 2012, the easiest way to fix this is by some quick tuning with a J3 chip.
The factory GT-40 and Cobra manifold are very similar to the Explorer, all use the same lower manifold. The GT-40 manifold was used on the EB GT, EL GT and NL Fairlane By Tickford.
Another factory option is the intake manifold used on the 5.6L V8 AUIII FTe 'T-Series', commony referred to as T3's. These have 8 long trumpets used to fed the cylinders, and a large plenum. They came standard with an 82mm TB, and have had very good results on modified engines. The problem is they are very rare, and if you find one for sale, an asking price of $3,000 is not unrealistic.
When looking at aftermarket manifolds, many companies make them to suit the 5.0, and on most the upper can be reversed so that the throttle body sits on the LHS/passenger side of a Falcon. A notable exception is the Holley Systemax manifold. All manufacturers advertise whether or not a manifold can be reversed.
Another option is to use a carby-type manifold with EFI injector bungs cast-in to each runner, fitted with an elbow and throttle body, instead of a carburetor. Carby-type manifolds are (sometimes considerably) cheaper than EFI manifolds, and produce good peak numbers whilst sacrificing low-end torque due to the shorter runners.
The standard E7-TE heads are also quite restrictive, however there is also a large amount of options to replace them.
The most popular option once again, is to use the GT40P heads found on the AU V8.
GT40 heads are also a relatively cheap option, although they don't flow as well as GT40P heads.
When you move to aftermarket heads, the options are simply as big as your wallet.
Trick Flow Specialties (TFS), Edelbrock, World, Dart, Air Fuel Research (AFR), Cylinder Head Innovations (CHI) and Ford Racing are commonly used brands that all make heads that will bolt-on to a standard bottom end without needing modified pistons.
Often, pushrods will need to be replaced with suitable length ones. The manufacturer advises what length to get, and often sell them in kits with heads, rocker covers, gaskets etc.
Changing the rockers from the standard 1.6 ratio to 1.7 or 1.72 ratio will improve performance without too much dis-assembly work. Caution must be taken when an aftermarket camshaft is fitted however, as the increased lift could push valves into pistons. Bad.
It's also worth noting that many aftermarket heads use shaft-mount roller rockers, which are incompatible with the standard heads stud-mount rockers.
The standard HO camshaft is, once again, quite small. The cam used in the EB GT, ED Sprint, EL GT and NL FBT is slightly larger, but the common choice and best option is to fit an aftermarket camshaft.
There are, as always, a massive choice in camshafts on the market, but not suit all applications.
Ford racing sell camshafts, including the E303, F303 and X303. While they aren't a bad choice, they were designed in the late 80's, and the trend nowdays is towards camshafts with larger exhaust lobes/smaller intake lobes. They will generally be 'lumpier' but not make the same power as a modern camshaft grind.
Common aftermarket choices include the TFS "Track Max stage 1" (TFS1), Crane 2030
When changine camshaft, it is advised to change the timing gear and chain to a double-row one at the same time.
A major thing people claim sucks about the Windsor is the weakness of the standard block. It's well known for splitting when power levels are substantially increased, however there is no set limit for it happening. 500bhp is about the safe limit, but there are many things that affect the block strength, mainly RPM and the tune.
There are many cases of cars making well over 600rwhp/450rwkw and lasting for long periods on US cars. Nearly all of these are turbocharged though, are well tuned and don't rev past 6,500rpm.
A mains cap girdle does nothing, despite what anyone says. All it does is hold the engine together in case of a catastrophic failure where the block splits completely in half, which has happened. This is all well documented on many US forums.
As of 2012, no-one on BoostedFalcon.net has split a stock block, despite vehicles making in exces of 300rwkw and completing many drag passes/dyno pulls etc. The first person to accomplish this feat will surely be celebrated.
The 5.0 responds very well to boost, with many members on here running their own single turbo, twin turbo, positive-displacement superchargers, or centrifugal supercharger setups.
There are many single and twin-turbo kits sold in the US to fit the 5.0, many for under US$1,000 using China-copy turbo/s. However, the exhaust manifolds usually included in the kit suit Mustangs, which generally sit too close to the ancilleries to bolt-onto a Falcon. The manifolds can be modified to suit however, just something to keep in mind.
Kenne Bell sell a range of positive displacement superchargers to suit 86-95 Mustangs too, however these also require some modification, with new fuel rails and a custom throttle cable needed to suit Falcons. The inlet/Throttle body also sits on the RHS/drivers side of a Falcon, so modification of the battery location will also need to be undertaken.