Hello, and welcome to the forum, sounds like you have been busy, and are off to a good start on reviving your truck.
I would try searching all of your info requests, there is plenty of info on this website.
For your diff, 4:11 gears are going to wind this old truck up fast, have you considered looking for a complete carrier with 3.73 or 3.55 gears. On my 1955 Fargo pickup, I have a late 1980s mopar 8 1/4 diff with 3.23 gears, makes highway cruising much nicer. The swaps are no that difficult, I do not have a parts suggestion, but hopefully someone will chime in....good luck