Ok, updates for anyone wanting to do this swap:
1. you’ll need to space the caliper in, two spacers id, 8mm, od 18mm, L 7mm and get two M8x1.25 40mm long bolts.
2. you need to ovalize two of the six rotor bolt holes slightly to get the stock long bolts through. Then you’ll want to drill four new holes based on the 6 bolt rotor pattern, tap them 8x1.25 and buy four bolts 15-20mm long.
3. you’ll need two new axle spacers (this does not accommodate speedo drive) id 15mm, od 22mm, Length for right side 25mm, length for left side 21mm. You need to remove the VTR250 speedometer drive stop on the fork leg (or at least shorten it a couple mm).
4. You will need a steer tube donor.