The W2's with 3/8 (2.02 valves) will easily flow over 300 with porting work so decide how much performance you need from there. I was extremely happy I didn't spend the extra money to upgrade my valves after my W2's cracked. They are now "leaners" along my garage shop wall.

1970 Duster
Edelbrock headed 408
5.984@112.52
422 Indy headed small block
5.982@112.56 mph
9.42@138.27

Livin and lovin life one day at a time