It's always good to hear another Heavyweight Robot is been considered to be built.

If you can get those motors for free you should and 2 speed controllers from 2 would be ideal-

that way you could either have 4 wheel drive or at least an independent controller for both sides.

I imagine the controller is lever or twist grip so save that too-you may be able to run it from a auto

return servo to keep costs low.

In terms of power most good Heavies scoot across the arena in 5 seconds and weigh 110kg

just to give you an idea