Use a 2-sheave damper for a 250 6 cylinder. They're on Ebay brand new for under $50.00. It's necessary to shorten the snout by 1/4" and machine the OD back the same distance to make the belt grooves line up properly- - - - -or throw a big chunk of money away by dealing with damper Dude.

Hydraulic/electric was NOT one of Ford's better ideas. The idea didn't last long in production, and 35 years later, it hasn't improved any.
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!