There are basic differences in all four tubs - MB, 2A, 3A and 3B.
Each tub moved the driver seat away from the dash a little bit compared to the previous model by shortening the wheel housing. So 2A has slightly more room than MB - 3A more than 2A - you get the idea.
Even the 3B with the greatest seat back to dash dimension is too small for some guys and they've done what Nate suggested - cut back the wheel housing.
I've never heard of any flatfender owner complain of it being too big for a small driver. I've seen pics of kids driving them with no comment on the kid's legs being too short. I'm 6' tall and my 3B is a little bit cramped. My 2A is a lot cramped.�
