What is the width from backingplate to backing plate on a 1992 rs 10-bolt camaro? What about a 4-th gen from backing plate to backing plate?

The 4th gen rears are 3.5" wider plate to plate.

Someone will try to chime in & say 4", but that is based on this......

Since our stock rear wheels set in a bit more than the front, that's why the typical adapters used to put 4th gen wheels on a 3rd gen axle, is a 2" one on each side (for 4" total).

If you wondering about putting in a 4th gen axle & keeping the stock wheels, they end up sitting PERFECT (IMHO) in rear.

Im wondering the measurement of it though because i found a ford 9-inch in a junkyard that measures 57-1/8 inch from inside of backing plate to inside of backing plate and im wondering if its worth picking up.

62", according to my 'net searches.

That 9" would make for a good narrowed rearend, but require you to get new wheels.

I doubt the trailing arm mounts are that close together, so they *shouldn't* interfere, IMHO.

The fourth gen diff is no stronger than your 92 diff. It's just wider.

A junkyard 9" that's the correct width or close enough, isn't an easy swap. Third gens use a torque arm suspension and you need to find some way to attach the torque arm to a junkyard diff or eliminate it with a different suspension system such as ladder bars. Unless you have good fabrication skills, it can be cheaper to just buy an aftermarket bolt in diff.

When looking for a junkyard diff, you should be measuring axle flange to axle flange. That's where the rims sit so that measurement will determine how well the tires will fit under the fenders.

Ford cars have a smaller wheel bolt pattern than Chev. Ford trucks have a larger pattern. You'll either need to buy new axles with a Chev bolt pattern or use rims with a Ford pattern. There's also brake changes. It's not easy to install Chev brakes on a Ford axle so using Ford brakes means it's easier to use rims with a Ford bolt pattern. An aftermarket diff is designed to use the Chev brakes making it an easier bolt in.

My 9" uses Ford drum brakes. 11 x 2-1/4 are much larger than Chev brakes and I found lightweight drums than don't have the huge cooling fins on them. The only changes I had to do was drill out the wheel stud holes in the drums to accept the 5/8" wheel studs that I use. My ProStar rims are in the smaller Ford pattern.

If you find a diff that's a few inches shorter, you just need rims with less backspace to keep the tire centered under the fenders. My old 10" wide rims have 5.5" of backspace. I now have a narrowed diff and my 15" wide rims have 5.5" of backspace. My axle flange to axle flange measurement is 45".

Thanks for the input guys, this is an ongoing prostreet build. Fabrication is no prob for me and i have some brake ideas in my head that i think will work. Should be a fun project sence this car is FAR from my daily driver and there is no deadline at all on it. Thanks for diggin yall!