The simplest way to get a double groove damper on an early stovebolt engine is to modify a 230/250 balancer so the belts line up. Those balancers are available everywhere for less than $100.00 each. The snout MUST be machined to match the stovebolt hub dimensions. That's probably what the D/D "economy" balancer is. They're still committing highway robbery with that one!
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!