As a thought exercise I've sketched out a concept of using two engines. One powers each track through a transmission. Turning is by varying the engine speed(s). Shifting the transmission is by a linked shifter so each transmission is in the same gear. The link could be disabled allowing one transmission to be in reverse for spin turning.
Manual transmissions would be the most efficient, and would be clutched by one clutch pedal.
Looking at the industrial yanmar diesels (40+/- hp ea) two side by side would be a fairly easy fit. The electronic common rail fuel systems are very responsive and reliable. By staying small the lighter aluminum block can be used as opposed to going a single larger iron block engine.
Don't really think it would be practical, but I don't think it is any crazier than some of the stuff that has been built.
You can do it with one power source and a splitter gearbox, but now your back to
The 4T Thiokol drivetrain basically