Since wheels are rated for each wheel, and a cab wouldnt weigh over 400 pounds, you can get away with 125 pound rated wheels.
The reason for the cab cart for me was to go from sandblasting to finish paint in one tool. This meant putting 8 inch wheels so I could hitch up the cart and pull it outside with my lawn tractor. Turned out to be good on concrete then too. Once you go with that large of wheel, weight isn't a factor since they are usually rated at about 400 pounds each.
