Hi Gary,
oh if only there was a taller ratio than 4.63 available! Unfortunately, there is nothing taller than that for your rear axle. Which leaves a couple of options. Change to a single wheel rear end; some later Falcon ute diffs are about the right width. If you want to retain the dual rear wheels you will have to cut the centre out and fit a Falcon BW or 9 inch centre to the Transit axle tubes, and get a pair of custom shafts made. Another option I am exploring is fitting a Mk7 rear axle. It is only about 50mm wider than the Mk1/mk2 axle, and can be had with ratios up to 3.3 if I recall. But you will struggle to find the taller ratios in NZ, and probably have to import one from the UK . Also, you will need to fit the 16"wheels from tne Mk7, to clear the disc brakes, and because the stud pattern is different. There's a couple of options for you to consider, unfortunately none of them are super easy! I have a Mk2 with Supercharged V6 fitted, and am facing a similar dilemna!
Your camper should go well with the XR6 engine in it!
Conrad