I understand that 88-up 10 bolts came with 28 spline axles. Is this the only change for 88? Can I take a pre-88 rear and install 28 spline axles with a 4th gen posi unit and bolt it up to my 91 RS?

And also: How practical is it to swap disks to a drum rear?

 

89 was the change year and most were still 26. yes you can swap a 28 spline posi in to your rear and add axles that match with no problems.

 

Did the size/quality of the disk brakes change at all from 82-92? Also, what other cars came with rear end with all the same provisions and same size?

 

Disc brakes changed from the problematic iron Delco Moraine calipers with the aluminum PBRs in 1989.

No other cars came with the same provisions and size.

 

So is it a worthwhile upgrade to buy factory 1991 Z28 front and rear rotors, calipers, and pads, and put them on a pre-'88 car? Everything bolts up, e-brake mechanism, mounting holes, etc?

 

I dont think the fronts are any bigger unless you find the 1LE package.