Finally found a set of BF Goodrich Radial TA's (215/65/15) and Billit rims for the 85 from a buddy. They look great and fit perfectly. My next project is a posi rear. The 85 has the stock 10 bolt open rear (2.41, I think?). My question is what other drum to drum rear ends will fit (Monte's, Malibu's) and how can I id them at the local bone yard? Specifically what model year. Would it be easier just finding a posi unit and installing it to the stock rear (along wiht changing the gear). Thanks for the help again. 1985 350ci, TH400.

My question is what other drum to drum rear ends will fit (Monte's, Malibu's) and how can I id them at the local bone yard?
Any 78-88 G-body rear end will fit in your 85 Elky: Regal, Monte, Malibu, Cutlass, Gran Prix, etc... Lots of wagons came with posi rears too. Look for the "G80" RPO code on the Service Parts Identification tag in the trunk. It indicates a posi rear end.

Look for this tag attached to one of the differential cover bolts. This tags came from the factory on posi differentials. If the tag is there, there is a good chance the rear end is a posi. However, the presence of a tag is no guarantee.
http://elcaminocentral.com/users/elcamino/poistag.jpg

If you find the G80 RPO and the posi tag on a car, you probably found a posi.