It should have a 206.8 C.I. three main bearing engine (sometimes called a 206 and sometimes a 207). A 235 is not a drop-in, but there is info on the swap in this site's archives. The good news is that the 207 is longer than a 216 and the 235 will fit in the engine compartment without moving the radiator.
Stopping the truck quickly in modern traffic is a problem with the original mechanical brakes.
Baldy
