I'M Back, LOL!

[CHEVYRULS]

The last 2.5 years I been doing Chemo and have just been revived from a Stem Cell Transplant, Ya it sucked but Im doing better now.
For the last few years im pondering the idea on what to do for my 1970 Chevy C10 Step side. My friend Bob hooked my up with his farm truck, and the thing is premo accept the 307 is shot and it has that puke Yellow color.

I managed to get a SB 400, Internally Balanced, as a replacement engine and now i'm trying to figure out what tranny to use. Presently I own a TH350 truck tranny and a 400TH both are a good used tranny, the 400 has a shift kit in it. The truck comes with the factory Muncie top loader 465 and im not to sure what to say about using this set up, so im looking for outside input before I start work on the project.
I don't know what the gear ration is because I have not been able to check it out but I don't have a problem about changing the gear ratio.