I do agree that the ISB is probably a bit of overkill for the 60. AS far as effort from what I understand the engine fits rather well and is about the same as doing a 4BT. There was a customer that brought a FJ62 into the dealership I used to work at that had a 6BT but he went with full width 60's, NV4500 and an Atlas. He was on 37" tires and was claiming roughly 25-27 mpg. Two reasons I want to go with the ISB is for the mileage and the power to haul or tow large loads. My initial plan was to put a VW TDI in my 90 4 runner and do a solid axle swap. After realizing the cost of that conversion and a few trips loaded up with one passenger and the dogs I realized I needed more room. I traded my pristine 4 Runner to a friend for his 83 FJ60. The 60 has at present a Ford 302 with stock 60 running gear. It is a fuel chugging, slow and hot running beast. I then purchased the donor truck that we retired from our fleet for peanuts. The drive train is in great shape, the rest of the truck is falling apart. As far as doublers I have not found anything to connect to the 47RE yet. I spent about 40 minutes going through possible options with Advance adapters. I am considering swapping to a NP205 with a 203 reduction unit. That would get me the proper front drive line exit but still stuck with a centered rear.
85 VW Jetta turbo diesel
83 FJ60 soon to be diesel
"If ye love wealth better than liberty, the tranquility of servitude better than the animating contest of freedom, go home from us in peace. We ask not your counsels or arms. Crouch down and lick the hands which feed you. May your chains set lightly upon you, and may posterity forget that ye were our countrymen." -Samuel Adams-