First Tamiya truck build, MACK Dump truck 6x6

[TRUCKMAKER]

It can be done but it takes a lot of modification to do it. Based on the wheel base your working with, moving the 3 spd back and modify it is going to take up space needed for you dump mechanism unless your going hydraulic, then you might get away with it. I would ditch the 3 spd before I'd get rid of the driven steer axle idea.
I'm on this kick about replacing all my 3 spds because they are a pain to keep adjusted and pretty much worthless in the big picture. They also take up way to much space that can be used for other stuff. Good luck and keep the pictures coming it'll be nice when its done.