Transmissions for dummies?

[ahoke]

New to the auto world and have been curious about the different options for 350 sbc transmission. Have a '70 GMC 3/4 ton I will be restoring once the snow melts and just curious why people swap the th350 out for a 700r4. Been trying to find a useful YouTube video but the search function these days is just overly targeted towards watching trash sponsored videos. The videos I do find are overly technical and glance over the simple aspects. In someone could list a few transmissions with a couple pros/cons would be much appreciated.

In short, I will most likely stick with the th350 that's already in the truck, but for daily driving/long distance trips, what's the ideal transmission? Not looking to win any races but the ability to comfortably cruise at 70mph sounds dreamy.