I picked up a really straight 1949 Chevy 3100 a couple months ago. I was also fortunate enough to find a GMC 302 from a ‘56 work truck. So, now starts the build! Still trying to decide on transmission/rear end.

Matt, First you have to set aside the second Saturday in January and go to the Northern Nevada Inliners meeting. You'll find a great group and people who have been doing what you are doing for a long time. When they see what nice guy you are there will be lots of support.
My '53 has gone through a few trans and rear end set up. It had a truck 4 speed and a Saginaw 4 speed. The current T-5 is the best. The rear end is a limited slip Dana 44 with 3.54-1 gears, a near bolt in. My engine is a '57 270. Here is a some info from another site on rear end choices. Tom
LINK

302AD, We missed you at the Northern Nevada Chapter meeting Saturday. I hope you can make it in February on the second Saturday. I was talking to one of the 302 Gurus about your project.