K25 suburban manual to Automatic swap questions

I bought a 79 suburban k25 for $800 a few weeks ago and I've decided I'd like to switch it from manual to an automatic. I don't know much about the truck yet, but the engine is a 350 that is not original to the truck and the tranny is a 3 spd with a granny gear (first gear is compound low, which makes me wonder if the truck originally came with a 454 under the hood). I would like to swap to at least a 4 speed automatic, preferrably a 4 speed with overdrive.
What transmissions will work with my engine and transfer case?

Probably your easiest thing would be a 700r4, you will need something to run the lockup converter on it. Everything else would be electronic and you would need wiring and computers for them. Also if you would want to opt with a 3 speed, get a 350T or 400Turbo, they are stout and will do you good.