Help...switching out rear end on 1965 C10 Stepside

[DBRENNAN5876]

Well here is the story...I have a 1965 Chevy C10 Stepside, and I am switching the front two a 5 lug disc brake. I already have all of that figured out. But I just started figuring out the rearend in order to get a a five lug in the rear. I found a five lug rear end off of a late sixties early seventies fleet side chevy. Now they have the same number on the left side of the pumpkin when looking at it from where the shaft hooks up. However, the number on the right side my original rear end out of my truck is GM 56 where as the new one is a GM 57. They both have the trailing arm mounts, and the control arm mount on the bracket in the right location. When measuring from the pumpkin to the end of the axle I found the new one to be an inch longer on each side of the pumpkin in comparison to my original.

Will this still work in my truck even though it has an overall greater width by 2 inches? I realize each tire will be out an incyh farther, but they still will fit inside the step side fenders i would think, but im not sure about tire alignment with the front tires.

Thanks, Drew