b body rear end questions,a body rear upgrade

I have a 63 valiant i am doing a v8 swap. Currently i am gathering parts ,info and having a 360 built.
My question is i found a 73 satellite being parted out. Its a 318 4 door car.
I understand it is wider and the perches and shock mounts will need to be moved to a body specs .
With the wider rear and everything moved ill get the proper offset etc and run wider wheels.
At first i thought it was a 8.75 so i paid the yard 150 bucks for a complete assembly. The car was registered last year so it is prob in good shape .
After reading a while ago i discovered they also came with 8.25 rear ends .
The motor i am having built is not over 350 horse. And i will have a A833 4 speed .
If it is a 8.25 any ideas on durability compaired to a 8.75 rear end. And any other issues i might have missed ?