ACW - Welcome to the board. I'm sorry I can't help you with your prop question directly and hope another Helms 30 owner can help.
The only thing I would recommend is to use a manufacturer/dealer that will work with you on swapping props until you dial it in at the rated rpm for WOT (wide open throttle). You don't want to damage your new engine in the long run by having the wrong prop.
Another thought to get you close would possibly look at what is used on a Catalina 30 with the same engine.
Rehoboth Bay/Indian River, DE
S/Y KJ, Helms 25