W2 valve size recommendations

I would start out by researching the part number and seeing if they are the ones probe to cracking. Mine were so I stuck with the stock 2.02 valve and mildly ported them to slightly over 300 cfm. If you are good at porting, taking them to someone good at porting, and are going to invest in a good set of rockers I would go with a 2.08 valve and try to get 330 cfm out of them. W2 heads have a
beautiful short side so it would be fun reaching for the moon on a set.