I think it would be much easier to change it to 12 volt period. Get your bulbs, resistor to gas gauge and a 12 volt alternator or generator. You'll love it. It will start much easier with 12 volts.

-Tim
'51 Chevy 3104 w/'56 235, 848 Head, HEI Dizzy, Corvette Cam, Split Manifold and Dual Carter YF's