With a couple of minor exceptions, all Chevy 1/2 tons are 6 lug. 3/4 tons are 8 lug. In the early 70's 5 lugs were used on 2 wheel drive trucks for a time and then went back to 6 lug. They are still 6 lug to this day. So the 67-72 series were the only 5 luggers out there.
All 60-66 1/2 tons are 6 lug whether 2wd or 4x4.
Check out Woogeroo's tips on 60--6 trucks on these pages before you go look at the 3 trucks. The best advice I can give you is, if the overhang over the windshield is rotted, walk away quickly. Pretty much everything else is correctable, but that area means the cab is pretty much terminal!
