Thanks for the input. It sounds like I’ll be ok starting out with the stock radiator and seeing what happens. I had read about the water pump issue and it sounds like the adaptor is the best way to address it.
I was debating about changing out the 216, but this will never be an original show truck. I figure I might as well make it a little more roadable with the 261. My next debate is whether to swap out the torque tube rear end to get better gearing to go along with the 261.