A 3/4" square drive fits into the hole in the damper and engages enough of the opening to turn the engine. Use a 1/2"-3/4" drive adapter on a 1/2" drive ratchet and you should have enough leverage to turn the engine, assuming the ratchet/adapter combo has room to clear the radiator and the fan blades.

Have you made sure the points are clean and the gap is set correctly? How about static timing? Once the ignition system is working properly, the battery cables are the right size, and the connections are clean and tight, even a 6 volt system should start easily. There's no excuse at all for a 12V system not to start if it's set up correctly.
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!