i am not sure i understand about "running a rear bogie with one half longer than the other." if you are talking about how they relocated the 3rd axle further back, I still don't see the harm. As long as the suspension is working (which it is).
If you define your rear suspension 'working' by the fact that the rear of the truck is suspended and there is a way to attach the axles, then I guess it works.
On the other hand, if you consider that the rear suspension is designed to have a center pivot for the bogie, with equal length torque arms front and rear, then maybe it does not. You have changed the loading on the center pivot, changed the scrub radius when turning, changed the fulcrum point for the springs, changed the articulation of the rearmost axle, changed the stresses, etc. etc.
Maybe you can run that way for 100 years with no problems. Maybe all it changes are the handling dynamics of the truck (hopefully, not for the worse).
My suggestion is that this is not the right way to do things and that setting up the truck that way is a bit slim shady. We've already seen that the PO added some hack factor into the building of that truck - for example, the cockeyed steering brackets. You know you have to fix that. Why should you accept that the rear suspension mods were done to a higher standard? Without knowing anything about the PO, is it possible he did things quick and dirty to make it look cool?
I am the first to admit that your truck looks awesome. I am honestly not dissing you or your truck. But if it were me, and again this is just the way I think about things, I would somehow address the unbalanced nature of that rear suspension (and I would not move the front axle forward).