I found a 90 cruiser at my local junk yard and its sitting so low all I can make out is the metal tag for a posi rear. What size 7.5 or 8.5 and what ratio did they come with and lastly will it be a good option for an 80 cutlass supreme

 

I believe the wagons had the 8.5. At least my 80's lesabre wagon did. 3.08 posi. was in it.

As far as going in an 80 cutlass, it would physically go under it, but would stick out a lot on the sides.

Gbody rears are 51.5 inches between the backing plates, and the wagon rears are 56 if I remember correctly. It would stick the tires outward 2 inches on each side.

Also, they have bigger bolt pattern circles on the axles, so you would need to take the 5x5 rims from the wagon too.

Also, when going from a 7.5" rear to an 8.5" rear, you have to shorten the driveshaft or find a shorter one to put in.

 

What J said. Much wider but yes an 8.5.

 

Thanks for the good info guys

 

That's true from about 1983-up. Earlier B-body wagons may have had the 8.5 or the 8.75 (good luck finding parts for one of those!).

And we're talking 6-7 inches wider than a G-body axle. The B-body wagon axles are even wider than the sedans. It ain't even close. I say this frequently. If there were a cheap, easy G-body axle swap, the factory 8.5 axles wouldn't keep being sold for stupid money. Supply and demand, folks.