After reading the post more carefully and then reading the forum description for the Engine and Driveline Shop, "The place to discuss engine items, rebuilding, updating, swapping engines, trannies, driveshafts and rearends.", it is my opinion that this should go in the Engine and Driveline Shop. I wouldn't call these motors "high performance". Just a bit of a rebuild, update and swap or so to speak. And for you purists, the 261 was available an option for my truck in 1962 and only in 1962. That's part of the reason I'm doing it.
The HIPO shop is supposed to be here for the hot rods and racers. My truck is neither.