I have done a couple of rear disc conversions using a custom bracket to mount R31 Skyline callipers to the hub flange. R31 disc rotors are also used. Can be done without pulling the stub axle (but after this many years, the bearings could probably do with replacing). The beauty of the R31 callipers is that they the simplest handbrake mechanism that I have ever seen (some calliper/handbrake setups are quite horrendous). I have several pics. if anyone is interested. Further, the inspection at Adelaides' Regency Park Depot, went without a hitch so I guess they were so factory looking that it didn't matter.