rearend swap questions

[Bret B]

First time poster, long time learner.

I have the said '65 below. Some number of years ago, I swapped out the original rearend for a '70 c10 5lug with 3:08 non posi. A few years ago, found some great original ralley wheels. When I put them on, the wheels tires wouldn't fit under the rear fenders, there was about a half inch sticking out past the fenders on each side. Since attempting to put them on, I took the fenders off to figure out what the deal is, but to no avail. The only thing I can think of is there is a size difference between the years I didn't account for or know about. Ralley wheels I got are 15x8 with tires of 255/60. Something isn't adding up in my brain here.

Heres the questions, are the rearends different sizes (backing plate to backing plate)? I was told there is a spacer or adapter that needs to be removed, but I don't see one, so where would it be? Finally, if the rearend I got came out of a '70 Suburban 1/2ton, is there difference there as well?

Would appreciate any assistance.

Bret