Are are 5.5" on 5 axles interchangable with the 4.5" on 5 9.250" axle? The A-Body cars they had different sized bearings w/big & small bolt which has nothing to do with trucks I know but just was curious

I believe there was an issue with the axle, or "C" clips, or the spider gears, or the pin that holds the spider gears between some later model rears and the early year rears. Unfortunately, I sure can't remember the years of the changes. It seemed one way would make the clearance too tight, and the other way made the clearance too loose. Gene

There are two issues.
The first issue is there is a difference in length in the axles ,about a 16th of an inch. The second issue is the c-clip, they are slightly different sizes and slightly different locations, but I took care of that by trimming some length off of the 4.5 bolt axles and making custom c clips

Check with Moser Axel's or Superior.

Ok thanx, were you going from small bolt to big bolt pattern?

From big to small.

A guy I know needs a big bolt for a an 86 and I have a small bolt from a 77 ramcharger which has the right gear ratio and thats why I needed the info