Welcome to Stovebolt!

Here's a good tech tip on 6V to 12V conversion; it helped me. It also covers pos to neg ground conversion. It might be helpful in figuring out what's going on with your truck, at least the ammeter reading.

http://www.stovebolt.com/techtips/12_volt_conversion.html

As far as the coil wired backwards, I don't know for certain. But if you're going to go to neg ground, just hook it up properly all the way through the system to remove doubt.

Best regards,

Bill


1947 3100 Advanced Design

Never, never, never, never give up. - Churchill