Thanks! I called over to CruiserOutfitters and they didn't have a great recommendation but JTOutfitters recommended using the master cylinder from FzJ80s as they were designed for cruisers with 4 wheel disc brake systems so I went with that...
Hey 60Works, just picked up the FROR kit with '17+ 4 runner brakes. In your other thread you used an Advics master. Do you recommend using that or a 17+ 4Runner master?
My rims are 4.56 backspace so I might be cutting it a bit close. Ha
I was looking into this myself. Didn't want to replace the rear axle. What about just converting the rear drums to disc with one of these conversion kits?
https://www.jtoutfitters.com/product/rear-disc-brake-kit-for-toyota-land-cruiser-fj40-fj55-fj60-fj62-fj80-conversion/