Welcome to the sight, you are sitting on a gold mine of information here. If you got the access to a welder I would consider making your own bumper, the one I made for my BJ74 cost me about $300 when it was all said and done. I run 35's with the stock 4.11's as a daily driver on my 74 and it works out great around town and allows you to cruise at higher speeds on the highway but it really powers out in the hills.
Mileage has suffered only slightly. I did 23mpg with 33's on my BJ74 (my BJ71 does 23.5mpg on 33's). I went down to 21mpg with 35's
I am assuming this is a RHD JDM unit running a 24volt system, so you'll need a good power converter. Depending on how many accesories you plan to run you may want to consider a solar converter. Here is a couple links to check them out
Solar Converters Inc.
http://forum.ih8mud.com/diesel-tech-...nal-setup.html