Axle question

[RED68SWB]

Hows it going everyone.

I got a problem with my rear drum brakes. They squeak like crazy. I got a 68 SWB with a 5x5 bolt pattern. When I pulled the wheels and drums off I noticed that the rear axle was about 3/4" longer on both sides than it was supposed to be, leaving my drums too far away from where they are supposed to sit. My pads are only making contact on about 75% of the drum. Its a 5 x 5 bolt pattern, so its not original. Does anyone know when chevy started with the 5x5 bolt pattern? Im just trying to see if any one has any idea what my course of action is. Im thinkin I need to replace the rear axle, or something along those lines.

Any advice would be greatly appreciated.

Thanks