Check the stamped number on the machined pad behind the distributor. Chances are the engine was originally installed in a car, not a truck, and the solenoid-type starter was correct for the OEM installation. Also check the bellhousing the starter is bolted onto- - - -are the bottom holes where the transmission attaches threaded? If so, it's a car bellhousing.
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!