I got a couple hours in on the project bike this weekend and managed to get the GSXR front end mounted up. It went on surprisingly easy and didn't need as much machining as I thought it would.
The XT500 stock has individual ball bearings in the steering stem. I bought a conversion kit for taper roller bearings that comes with the 2 bearings and 2 races to press into the frame. Luckily the steer tube bearing diameters on the GSXR triple clamps are the same as the XT500 so no special machining needed there.