the simplest way to tell is is to look at the battery cables. since i own two gmcs and one chevy and i thought it was a no brainer. for my vintage its easy because gmcs are pos. ground and chevy is neg. ground. NOT! when i was removing the old wiring or what was left to it in my 40 i started at the wiring and not at the battery while tracing and removing each circuit. at the end of the process i noticed that a PO changed the polarity from original pos. ground to neg ground and its was at the battery is where i noticed it.
why would someone do that?
since i had a 6/12 neg ground converter available i left it neg ground and installed the converter and hooked up my sound system to it. it saved me the cost of another converter.
a guy local to me has a 35 international and goes all crazy about the pos. ground thing. he'calls me all the time when there's electrical work to be done on his truck.
