You can do that, but it would be much easier to just use a voltage reducer (think diode) from 12v to 6v. Much has been written about that here already. Come to think of it, I believe I might have a 12v motor that would work there. It is in the attic, though. I'll try to remember to look before it gets too hot up there some morning.

~ Jon
1952 1/2 ton with 1959 235 | T5 with 3.07 rear end