Mika,
I have seen several lists, and certainly organisations like the Abarth Register in the USA have accurate information on member's cars.
The problem was that Abarth did not keep meticulous records of the car manufactured himself. Perhaps for good reason as rumor has it that this may have had something to do with homologation "games" that were undoubtedly played.
Further, Abarth did sell many "kits" to update existing cars. I have seen early TCRs with all steel bodies. Then again the very late cars had fiberglass fenders and noses. The last TCR model even had a very special rear suspension that looked to be very close to a double a-arm setup.
As far as the mounting location for the oil filter goes, I believe the factory location is in the area where the original rear radiator was located, down low. Mine is located very close to the same location but a little further rearward. I have seen others that are located quite high up on the right rear engine compartment side panel. In this case the car may have been a TC (single down draft carburetor.
I have been racing in the Abarth Coppa Mille series for a number of years now. Here at least I have found a home for racing that allows replicas to run. Yes, mine is definitely a replica.
www.scuderiatopolino.comKind regards,
Paul