GMC's in '37-'38 used a 60 psi oil gauge, it fits in the same opening, but the decal colors are different along with the numbers. If you are good with photo shop, it would be easy to make the right color decal for one.
You can also adapt a new 100 psi gauge to the old face plate. It wouldn't be that difficult to do if you are handy. E-bay all ways has old gauges for sale for these trucks if you want to save yours. 36-38 trucks and some cars used the them. I stuck new gauges in a '65 GTO dash, all it took was pulling the old ones out and finding new ones with the same sweep. I hot glued the old dial over the new ones.
By the way, I have been running mine over 11 years with the stock oil gauge and I know from testing the engine has 50 to 60 psi oil pressure. As long as the gauge is off zero, I don't worry about. With it hot out and 5-w-30 oil, it drops to 15-20 at idle, when its cold, its all ways pegged.
Amps shouldn't be a problem, you should never see full alt load at the gauge. My truck uses a standard GM alt. 40 or 50 maybe, and I have have never seen the gauge dial more then 1/8" off center. The only time you would ever spike the dial is a dead short.
Joe
