Was the '38 olds originally a pos. or neg. ground? Working on my son in laws car and i went to hook up the 6 volt battery out of my model a and noticed, making the assumption that it was neg. ground, that i had to spread the pos. terminal clamp quite a bit to get it on the post unless i was hooking it up wrong. I thought GMs were neg ground. Anybody?
'38 Olds should be negative ground, all 6 volt GM cars were neg ground, Ford and Chrysler 6 volt cars were positive ground... if the battery has been hooked up backwards it is likely that you will need to flash the voltage regulator to make it charge properly again. (touch a battery lead to the field terminal momentarily)... good luck