Find a wrecked F-250 with a 351/ZF tranny and throw that in! That'll make a work truck out of it.

First, I wouldn't necessarily go for a rebuilt engine in this truck. I'd go for a used engine that I confirm has good compression (150 or so) and good oil pressure.

That way you know the motor is in good shape and you can put it in without a real worry.

I don't recommend jasper engines, or many of the high-volume mass produced reman engines. You can do searches on jasper to find out, I talked about them recently in this forum.