Try some larger tires on those, the wheels look a little undersized for the cars.
A little trick I use alot when I want those lowpros to look large: take the tires off and put them on in the reverse direction. There's a little lip on the inside edge of the tire which you can put up on the rim, making it seem like there is more tire than there really is.
The ML looks very nice btw, gotta love black and chrome! :coolpics