Brilliant as my father would say that's "proper modelling" it must be great to have jobs you can really get your hands dirty on

Well, once you've got all the driving wheels out then there's nothing to stop you putting new frame spacers in, then cut away the ones presently stopping you driving another axle. That way you keep the alignment 'as is'. Good luck with the project.

Mark

As Mark says above I would look to modify the spacers and drive on the rear axle.

Looking at it, it is just the removal of the round spacer infront of the rear drivers, and have the gearbox facing forwards and the motor pointing vertically. Easy to compensate the front two pairs then, with a central beam. Pivot beam a couple of mill from centre towards the front driver. This will let the middle pair move up and down easier.

Yikes... that looks frightening! I can't comment on the what/why regarding the project, but it'll be fun to watch. All I can say is good luck... and I'll watch from a distance.

Jon