Are there fork options that accept the GS500E wheel/rotors without major effort?  I'm starting a cafe racer build, have a spare set of GS500E wheels and rotors... but no forks, and I'd rather something a touch beefier than GS500E 37mm units, ideally with external adjustability?

If you're going to want beefier forks I would assume that you'd want beefier brakes we well, so you might do best to find some meant for dual front brakes. I know the plastic cover comes off on the other side of the wheel, so it might not be too hard to work that out.

Do you know anyone with a lathe? Just about any fork will take any wheel assuming you make some new spacers for it.

After running the later style GS500E caliper with a Daytona radial master and steel braided line, I was astounded by the stopping power one could get mating that caliper with a good EBC rotor and GFA compound pads.  No problems hauling the GS down from any speed in very short order.  I imagine EBC's new EPFA pads would be an improvement over that.  So I don't mind a single caliper setup as long as the caliper is supported by modern pads.

a katana front end swap will do that.  uses gs wheel, with katana rotors.