1968 Short box

[New Bob]

So I picked up a 1968 2wd coil spring shortbox and I was hoping to get some help/information since this is my first project truck. The truck has a 5x5 bolt pattern and front wheel disk brakes. I realize these don't come stock with a 5 bolt pattern or disk brakes. The old owner is not available for comment so I was wondering if there is a way to determine what rear end is in the truck. I know commonly the 1971-2 chevy rear end can bolt in to swap from 6 lug to 5 lug. What I really want to know is what drum brake rebuild kit I can buy for the rear brakes and if there are some serial numbers I can use to figure out what is in my truck? I would appreciate any advice or experience shared. Thank you