Probably a small block Chevy engine will fix the go cart,
Regarding the HF tach: I have found most of their tools to be fine for occasional use but not for frequent usage. So I would give their tach a try. they are pretty good about returning anything defective.
I have been purchasing from them since about 1980 and they are a great source for inexpensive tools but you have to realize you get what you pay for.
The US General line of tool chest that they sell are a very robust product. I have a few of them in my shop and think they are the most bang for the buck. They fit in nicely with the Snap On, Proto, Husky and Craftsman boxes
