it's not so much the radiator leak (if so) I'm worried about it. It's if you think I should try just replacing the speed sensor or of you think it's obvious there's something in the dash causing the speedometer (and probably temperature gauge) to not work (which would be more work than it's probably worth since I'm basically salvaging this truck for parts.

There probably IS a radiator leak but temp gauge never showed HOT engine. What felt hot was the dial on the console for turning the heater from red to blue, I just felt it never be that hot, then checked radiator coolant level was empty (engine cooled down) and refilled and few days later the reservoir is empty again. Drove it 2 hours since refilling the 2nd time and level is good but still felt some heat on that particular dial area. Been 95 degrees out too.