front suspension help

[btp76]

I have a 72 SWB with a hole rusted in one upper control arm. I already have a rebuild kit from pst and 2" drop spindles for a 72. I also have a complete 68 front suspension, a 70 parts truck, and a disk front end that came out of a 68 parts truck.

My two questions are;

What is the same / different between the 68, 70, and 72 front ends?

Any way to identify the disk front end out of the 68?