How much can valve head OD be cut?

Another silly question: How much can be cut from the OD of a 2.02" valve head? Similarly, what is a good minimum width for the seat for moderate street use?

The reason to ask: I'm trying to stuff AL heads onto a bored 273 block (like Promaxx or Edelbrock) and am seeing a possible issue with the bore notches for the 2.02" intake valve. The pistons' top ring travel is coming uncomfortably close to the bottom of the bore notch with the valve lift I want to use.... like .010" or less if I have any sort of margin for valve float. So I'd like to see if I can do away with the bore notches, or have just a tiny bit at the very top. There is adequate meat in this block that I can shift the bores over and gain .040" or maybe even .050" on the issue, but wondered if the valves OD can be cut down too.

Tnx.
I wouldn't butcher valves to try to put a 202 valve head on a 273. Those 1.88 valve heads that AJ talked about sound like a smarter move.