My 79's speedo gear had broken teeth. I couldn't find another(steel) to match, so I simply purchased an inexpesive GPS and mounted it. Quick fix and it's functionable. Plus, your never lost out in the elements, as long as you have satelite recep. If anyone does this, make sure you get the power cords for hook up to vehicle battery, they eat disposable batteries quickly.
One thing is for sure, I purchased an autometer fuel gauge w/ the proper sender(ohms) and have nothing but problems. It never reads the gas level correctly. It's reads full most of time until it gets under 1/2 tank(actual) then it works until it gets to 1/4 and stays there for a while, then starts to move to empty as I approach it. It sure sounds like the wrong sender, but I was assured it was the correct one.