Here's a few historical things I keep in mind as far as interchangeability. not specific, but it can tell me if there's any chance of interchange when I look at something. It's some corporate history I use as a guide and has worked pretty well so far at the parts house and junkyard
Pretty much until around 1960 each division made substantially independent, individual cars. Most all departments were entirely independent in purchasing, production, styling, and engineering- therefore many parts differences.
1930's- GM introduced the letter bodies-"A", "B" "C", etc. to be shared among divisions. Even with that there are differences in exterior sheet metal and structure.
Late 1950's- Corporate tells the divisions to design their 1959 cars around the 1959 Buick LeSabre doors, due to tooling costs. Look at some photos, follow that fin line carefully, you'll see it...
1960-61- The real beginning of serious sharing. The Z-body Corvair and Y-body Tempest/F-85/Special share a lot more than you think. Of course the Corvair was unique being rear engine and air-cooled, but the Tempest rear transaxle came from the 'Vair- turned around and recased. Lots of body structure shared- my Corvair station wagon shares probably 3/4 of it's body with the B-O-P compacts. You can see quickly it has the same roof stamping and doors as the Tempest/F-85/Special wagons- nonetheless it has a different A-pillar. The engine compartment in the Corvair became the spare well in the B-O-P cars.
As models were redesigned in the '60's, the bean counters aggressively purused synergies. Production was consolidated as well with different makes, but same "_-body" vehicles made in the same plant.
The age of badge/grill engineering was fully established with the 1977 full size B/C body downsizing. After this this you'll find plenty of interchange as GM hunted savings in purchasing, inventory, and manufacturing- following the "Chevymobile" controversy, GM reduced it's engine types as well. By the 90's there was no real difference in comparable GM cars- only superficial stuff that met the eye.
So, with all that said,. the older the vehicle, the less it will share other comparable GM vehicles...
