I run a built 200-4R in my Chevelle and a built 700R4 in my C10. They can both be built to handle any reasonable amount of power. People tout the 200-4R as having a better gear ratio spread over the 700R4, but it is not as noticeable as one might think. I like both, really. I think the 700R4 fits a truck better if you plan to do any towing or other truckin' activities. It is inherently stronger and that lower first gear is certainly helpful when you're trying to get a load rolling. However, if you're planning to just use your C10 for scooting around and other hot rod shenanigans, the 200-4R is a good choice. It takes less power to turn, which results in a little more pep. Again, not by any huge margin.
Good luck and have fun!
(Be sure to set the TV cable correctly on which ever trans you choose!)