Info needed: Help to identify my engine!

[Alastair Thomas]

We have a F60S LAAT which came with the 21 stud 3.6 litre engine.
This engine lacks power probably due to some fundamental error during a previous rebuild such as the cam shaft being incorrectly timed.
We recently had the chance to buy a 24 stud engine in reasonable condition. However, on disassembly it turned out that it too is a 3.6 litre engine. We thought we had measured it incorrectly at first but found out that Ford of Canada did make a batch of hybrids.
Does anybody know if it can be bored out to 3.917 cc? We are told that this is not possible but that information may be based upon the blocks cast for the 3.622 cc engine in 21 stud form.
Confusingly it is stamped R3917 but callipers do not lie!
So far we have not found any other markings on the block other than a cartouche on the bell housing where we expected to find the engine number. I interpret this to mean that it is indeed a 3.6 litre engine.
Can anybody help please?
Alastair
F60S LAAT
Lynx I MkIII*