1970 C10 rear end questions

[69Tom]

OK, I've been running searches and not getting exactly what I want, so I'll just ask so I get it right:

(1) 1970 C-10 with a 250: what would have been original to the truck 12 bolt or 10 bolt?

(2) Original with the above, with a 3 OTT, 3.73 gears, correct?

(3) I'll be putting in a 402 with TH400. Best gear ratio? I'll be doing some mild hauling from time to time, but will also be driving long distances on highways. Was thinking 3.08, but wanted to make sure.

(4) Are there any good gear makers out there now, or am I best to go with a good used GM set?

Thanks for the help.