We used 2.125" intake valves in all of our race heads. I don't use anything smaller than 2.02" valve in the heads I do. You need to look at these engines on a volume level instead of it being just a lowly 6 cylinder. A 250 has the same cylinder volume as a 350, so a 2.02" valve isn't too big for it at all. It does require a little more careful bowl cutting, but you can easily get it to 80% of the seat size. We never struck water even with putting a 2.125" valve in one.
