Thats a good question on the diff!

It would be great if the rear ball diff can fit in the front.

I think the U.S spec car could well be an 'upgrade kit' for want of a better phrase.

But I think for now, this is all we have.
Also I think the foam car is declining and the rubber clad races are on the rise. Just like the Li-Po and Brushless stuff.

British Menace