Perhaps I am missing something, but why not elongate the wheelbase?
You already did the custom suspension, why not just get someone to slide it all back 50-100mm. It should not change your break over angle too dramatically if you did that, and then you have the added 25-60mm you would need to add that tyre and rack etc. Heck you could move it back half a meter if you wanted and really have room on the back for whatever you needed back there. I presume you may have to think about lengthening your frame to do this, but as you have already done so much to customize the truck, perhaps a frame stretch is not such a bad idea to get it where you want it. That and a new drive shaft and you would be good to go.
"Do you know what a soldier is, young man? He's the chap who makes it possible for civilized folk to despise war." -Allan Massie