1970-1981 camaro and firebird all have the same 8.5" ring gear 10 bolt at 61" from drum to drum.
1968-1974 nova are the same axle at 60" drum to drum
1982 and up use a 7.5" or something like that ring gear. they are weaker.
Any dana 44 yoy might find out of a jeep, an old ford, old doge etc... will have an 8.5" ring gear and be just as strong as the big 10 bolt chevy/pontiac rear
The ford 8.8 is comparable to the gm car 12 bolt
The chevy TRUCK 12 bolt has the large ring gear but the smaller pinion diameter of the 10 bolt.
The chevy CAR 12 bolt has the large ring gear AND a larger diameter on the pinion shaft than a 10 bolt
Oldsmobile and buick 12 bolts use different hard to find guts. the aftermarket stuff is mostly all chevy.
My own personal opinions
The 8.5" 10 bolt held up behind 400 horsepower big blocks- pontiac never ran a 12 bolt behind those 455's- all 10 bolts.
If I needed more than a 10 bolt I'd run a ford 9" or a dana 60 which are better. 12 bolts are over priced stuff for goldchainers and geeky purists ;D.
the 7.5" 10 bolt from 1982 and newer is fine behind anything under a stock 307. they even hold up for some people behind a 350 if it's not too powerful.
I'd bet a 9" or a dana 44 from an old ford pickup would be a good choice or if too narrow to fit the body between the tires
the 1975-1979 ford trucks have an axle 4" wider