The MadBull is perfect for "modernising", low centre of gravity, wide stance and still reasonable ground clearance.
The gearbox is pretty bulletproof as long as its ballraced but oil shocks are a must!
Motor wise, the world is your oyster.
As the standard kit tyres can "slip" on certain surfaces, acting like a slipper clutch, this together with the motor's location on the rear axle will keep the temps down.
You will benefit in looking to getting rid of the bump-steer up front, and the tiny axle springs at the rear....maybe think of the "5th shock mod" that Lunchbox/Pumpkin owners utilise.
It will stop the rear axle trying to do a back-flip when running hotter motors!
Have fun!
KingPin