Homer52,
Lets start with the serial number to identify the truck as American or Canadian. If it is American the 270-302 will bolt right in. If your truck is Canadian, you would have to move the radiator forward. Either way it should be a pretty basic swap. Since you have a 216 that is possibly original in there, you could easily swap a 235 or a 261. there is a trick with the water pump, to make it work.
Good Luck.
John
P.S. I'm with Cletis on the 270 or 302. I am putting a souped up Jimmy Motor in my 1940 GMC 3/4 ton.
