The rear is factory rear (needs rebuild also) in 90 d150
Like to have couple inches shorter each side. As I want to run a 10 wide wheel with least amount backspace on the rims

Don't know what is better option as doing 5he orignal 9.25. Or finding a wide 8 3/4 and cut t9 what I'm wanting

Will the backing plates interchange?
How much differance would be on drives haft if put a 8 .75 in it
Tia

The 9 1/4 has axle shafts with the "C" clips to hold the axle in the housing. Those rear ends also have the wheel bearings run on a machined part of the axle itself. If you remove 2" off the end of each axle, you will remove the method the axle was retained, and you will remove most of the axle splines, but then you probably will need to come up with a way to hold the axle in the housing because you never had the pressed on wheel bearings, they always rolled on the axle shafts themselves. I don't know if the performance aftermarket axle shaft companies have replacement narrowed axle shafts for a 9 1/4".

An 8 3/4 or even a 9 3/4 might be a better option if you want to narrow the rear end.

The brake backing plates bolt onto the 8 1/4, the 8 3/4, the 9 1/4, and the 9 3/4. And if the wheel bolt pattern are the same, the brake drums follow the same brake size across the axle choice.

So someone is going to tell you I missed something, I'm blaming my memory.

I knew about the c clips. I just fig could buy new axels to your length
Thank you very much

Might look at Dakota or Durango axles. Have to redrill the lug pattern but might be narrower.

The 9 1/4 was in all kind of vehicles over the years, And different widths/spring perches. Does yours have the tone ring?

I just went through this whole 9-1/4 narrowing exercise couple months ago. There was a Mopar Action tech article a few years back and it looked like a good option to a Dana. However, NONE of the big shops out there want to touch one. If you have the time and inclination you can probably do it yourself - all the good parts as well as axles are available. Check youtube - there are a couple good videos about narrowing them.

If the thing needs a full rebuild then I'd just opt for an 8-3/4 if it will handle your power - and anyone will narrow one of those AND you don't have the c-clip issue (which really isn't an issue in the Chrysler axle).

Will the backing plates interchange? YES

In the MA article they swapped out an 8-3/4 for the 9-1/4 and had to shorten the driveshaft. So if you swap in an 8-3/4 you'll need a longer one.

Another more pricey option would be to replace the housing ends with 8 3/4" Mopar and have a set of custom axle shafts made to use Green bearings..

Done one and honestly its a PIA...yes parts are available but Tooling (different that the typical axle housings) will be required to align the bearings if you decide to keep the needle roller bearing set up. You can get into a set of custom axles that fit the Green bearing and change the housing ends but custom axles are required. probably more cost effective to fins an 8 3/4 and rebuild it. depending on what you are trying to accomplish a B body rear with centered wheels works well with out and modifications. The truck pictured had stock rear frame rails, B Body axle, and 13" wide wheels.

I took this route on mine.
Dr Diff sold me everything I needed and had Dutchman axles drop shipped. Local shop welded the ends and everything bolted together.