Well, I would say that it "might" work ok, but the larger problem here is that if you are pushing more amps you are over stressing an already marginal wiring system. If you were to rewire it with larger modern wire it might work, but look at it this way, you are risking frying the entire wiring system at a minimum, burning the car to the ground worst case just because you don't want to bypass the gauge. I am the same way, if the car has it I want it to work, but when it comes to the amp gauge I made an exception just because of the risk. If I was running a stock or near stock alternator perhaps I would chance it, but with a 120 or larger, I am just willing to. Your car, so its up to you. I'd definitely carry a decent size extinguisher just in case.
