D100 Pickup question for you:

IMHO, it all depends what you are going to use it for. If you are going to use it like a pickup, with the leaning tower of power it would probably be a good idea to keep the transmission. Low gear can be a godsend. If you are going to use it as a driver and you have something against starting in second gear, then I'd just change transmissions and be done with it. IIRC there were two four speeds available in '62, the NP420 that has 3rd and 4th synchronized and the NP435 that has 2nd, 3rd, and 4th synchronized. Over the years, 2nd gear in the NP420 gets beat up and eventually won't stay in gear under heavy acceleration.

But good purchase. A '62 short bed Utiline is one of my favorite trucks.