If you've got "deep pockets" and a real desire to make the truck look original, there is a way to put a later model rotating assembly into the original block, and even increase the displacement to around 270 cubic inches. That requires some very creative (AKA E$$$$PENSIVE) machine work, however!
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!