That is a tough one. I also built a 431 for a guy and I used off the shelf Edelbrock heads and when I was checking piston to valve clearence I also noticed that the valve hit the cylender wall at about .600 lift. I ended up using a cam that is .550 lift and is only 247 @ .050 and it has been running now for a few years.
If you decide to do another engine nextime use a 400 block. it is the same deminsions externally as the 383 but the stock bore is 4.340. when you take it to 4.375 it is only .035 over and you have no clearence issues to deal with. This dimension piston is a common big block size.
Good luck.