Chevy is supposed to have Negative ground. That's why your ammeter is working backwards. Swap the battery cables, and re-polarize the generator. No other circuits besides the generator should be involved. Most recently-manufactured regulators will work with either Pos or Neg ground.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!