71-74 8.75 b body rear

but i have the later b rear end flange to flange is 57.8" perch to perch is 47.3" so u have to move the perches more than an inch.. i also want to put the willwood rear disc kit on it, and moser axles but that will change the offset, and idk if it will stick out too far then

I'm assuming you have a Duster by your user name. The B body rear will work fine. Some guys will tell you to pull the springs out a half inch on each side and bolt it up. This will work, but I don't like the geometry.

Where did you get 47.3 on the perches? It should be 44 from center to center. A body is 43. I moved my perches in 1/2 in on each side and shortened and balanced the driveshaft. I'm running stock Rallye wheels.

Here is a pic, it's in a Dart Sport.