EB Falcon lash adjusters getting changed from 11mm to 14mm

[Neil's Falcon]

Hi, I had noisy tappets on my 09/1992 EB GLi Falcon wagon which I gather is a common issue so according to a seller on eBay I bought 11mm lash adjusters but after taking the rocker box off I noticed that the lash adjusters in situ were 14mm so the ones I bought didn't fit. Upon further investigation the head has 91AA stamped on it so is this an indication of what the lash adjuster size would be? There are also discrepancies with engine as on the rego papers it states the engine size as 3.9L but the rocker box cover states 4.0L as does the side panel on the body. As this is my first Falcon I imagine these questions seem naive but I have searched internet quite extensively and haven't found a definitive answer as to what vintage my engine is. I also want to buy a fuel pump and other engine related items so I really need clarification on what exactly size the engine is
Thanks Neil