Probably stupid questions, but I really don't know

[don t. - 72gmc]

Currently I own a 72 GMC, 3/4 ton long bed. I have found on the web a 70 GMC 1-ton that seems to be in very decent shape.
Now for the stupid questions......
1 - How many others have bought a vehicle sight unseen? Truck is out of state and way to far for a weekend drive. The seller has sent pics, and they do confirm the decent shape.
2 - Im use to 350-4bbl engines. This is a 396-4bbl. Besides the obvious, whats the difference? Parts available? Anything I should ask but don't know about?
3 - What is an "open rear-end", related to the truck (grin).
4 - How hard is it to find AC parts? Seller says its all original parts are there. Personally, AC is not a deal breaker. I prefer 2-75 AC anyway(real big grin).

Thanks much.
I do appreciate it.

Have fun......don t. ......