what is the size of reamers that I need for oversize valves?
When I installed 1.66" diameter (head) and 11/32" diameter (stem) stainless Fordson valves in my '15 touring I bought a 5/16" adjustable reamer so I could achieve the clearance I was after. Then hone the guides to get a nice finish that will hold oil.
So first you need to measure the valves you plan to use. Then buy an appropriate sized reamer and hone. You cut the seats after you complete the guide work so the seats and guides remain concentric to one another.
Here is a good source for tools:
http://www.cylinderheadsupply.com/vakve-guide-tools-valve-guide-hone.html