I feel like the already awesome and huge roster of vehicles made for Blockland could use an addition of a bit more off-road styled, bulkier vehicles. Here's a few suggestions:
Baja Truck
A simple baja truck. The most nimble of the three with good handling, decent suspension and speed.
Rally Truck
A slow and bulky truck. Slow acceleration, can tip over, if you try to steer too hard.
Mud Plugger
A rather bouncy car, much like the freestyle buggy. Great on rough terrain, but not exactly a track car due to it's low speed.