I got a gear on my golf car I need to rivet on, I need the hardest strongest rivets on the planet, any ideas please

Plug welding it would probably hold longer most likely.

Post a picture of what you are talking about...

I've been working on golf carts for 6 years, I can tell you how to fix anything on an ez go or yamaha.... and I know enough to guide you on par car, club car, ingersol rand, or jacobsen carts.