Rear end diffrences

[Captainfab]

A '63 C10 will have a 12 bolt as will a '65 C10. Those are basically interchangeable, but they will have different panhard bar mounts and different length panhard bars. To install a '63 12 bolt under your '65, the panhard bar will need a slight bend at the end that bolts to the frame bracket. Otherwise everything will bolt up.

Changing the bolt pattern on the axles is not something the average guy can do in his garage. The original holes will need to be plugged and machined flat, as well as the hub register machined down. Then the new hole pattern accurately drilled the correct size for the new studs to be pressed into the flange. I would only consider doing this if the wheel bearing surfaces are in good condition. If you need new axles, you will also have to change the spider gears in the '63 12 bolt.

If you could find a '71-'72 12 bolt it would be a simple bolt in and already have the 5x5 bolt pattern. However they will be 1.5" wider than the '63 to early '70 differentials. A '73-'87 differential will also work, but you would have to weld on the trailing arm mounts and a panhard bar mount. These will also have the 5x5 wheel stud pattern and are also 1.5" wider.