Rear Axle options?

[Ndkshns]

Hello all new here, I have a 69 C-10 long bed. The rear axles were put in a short bed, I was left with 69 6 lug axles and front spindles, (The spindles were just put on to be able to move the truck around.) The front has the 72 cross member. So the front is easy and I plan on lowering the truck with drop spindles anyway. However when the swap on the rear axles was done we noticed that the rear gears were broke. So I have 73 - 87 truck sitting here along with a 96 rear end, Will one of these other rears swap in? I have the coil spring rear, and I know that some some of these trucks have leaf springs, so I got to wondering why wont one of these other axles work? This one has been in the faimly for several years, it was orginally my brothers and we did some trading. and I ended up with what is left. Can i just swap the gears and axle shafts?

Also Is there a way to go to a one piece drive shaft?