I know it's not much at the moment, the one mod I have done to this is added a second diff to the rear axle so both rear axles are driven, as I only have just bought this set, it was easier to do now then wait till later.
I modified mine with the second axle driven like you did here, added a steering lock, added drive and steering motors, replaced the original 4 cylinder inline engine with a V8, and to make the v8 fit I had to modify the hood.