As far I as I know the Chevy trucks were always negative ground. GMC trucks could be either....
About have to start doing some checking to find where the problem is.....
Might have been more of an issue with the truck being 6 volt and installing a 12 volt battery.... The gas gauge, lights, generator/regulator, ignition coil, heater motor are all ,originally 6 volt, unless someone has converted it to 12 volt.
John
