Axle and rims help

[Kalums]

I know that it has been addressed many times in this forum and I apologize ahead of time... But I just need a definitive answer that I have not been able to find in this forum or from the internet overlords... So here goes:

I have a 71 GMC K2500, It has the 10 bolt Dana 60, 9/16 studs/lugs (I'm 90% sure) It currently has only the outer rims of an early 90s Ford F350 on the rear axle, which line up perfectly with the front rims.
Question #1) Can I put the inner rims on too? It looks silly to me having the rear drums just hanging in the wind. (personal preference)
Question #2) 2011 and up GM wheels won't work w/o an adapter correct? 8x165.1 (old) to 8x210 (newer)
Question #3) I understand what "hub centric" means but neither of the rims I currently have appear to sit on a lip around the hub like my Expedition. Is this because it is an older style 4x4? Where the hub protrudes significantly farther out?

Thx in advance