Monzas caused a problem with swapping body parts around. Started with Jack Dolan and his 'car of many classes', but that is a lesson in history for those that wish to be long haulers.
Bottom line, if a body part is for a GM 'F' body, across the year range, then it is OK for use. Body parts for 'G' bodies, etc all fall into the same rules. This is all GM of course, Ford and others must meet the same criteria. It is up to the entant to prove that the stuff they use is legal stuff.
DW