I built the same axle for my 4Runner. For the perches I simply cut the top of the existing perch to the angle I wanted and welded a piece of steel to the top to match the needed spring width. I did slightly cut into the housing on the passenger side to get the correct spacing. Overall was very easy to do. Never bolted it in since I will be 3 linking the front instead of leaf springs.

Another option to consider is running IFS hubs to get a little more width and then you can run drop off rotors from a Tacoma or upgrade to Tundra brakes if your rims will allow it.

Also, FJ60 and 62 front axles both had disk brakes and are the same width.