DennisM - Since no one else has asked, I'm going to toss this question out. Your signature line says you have a 1940 Chevy 1/2 ton, and you said your engine is a 1940 235. What's driving the train on wanting to use the GMC electrical gauge?
You also mentioned you have a 12V system. Guessing since it's a Chevy that it's negative ground. Just saying that the significant lack of available electrical sending units is going to have you hunting for years (if not decades) and I seem to recall that the Chevy gauges are different than the GMC in appearance. Wouldn't it be much easier to use a correct Chevy capillary tube gauge for what you have?
