I looked online for those 6/12 batteries. No luck.

I think I'm just going to go the 12v conversion route. I've got the alt, can easily build a bracket, already have a heater resistor, already have 12v battery, and found a place that sells the runtz for $3ea. Seems like the cheapest thing to do.

I could probably sell the 6V battery (it's new) and pay for the whole conversion.

'40 Studebaker project Chevy 292 powered.
'51 Chevy business coupe 216ci inliner
Inliner's #5360