Alan, what you are intending is building an A10 engine in A7 crankcases which is no trouble as the cases are the same. Use a 356 or 357 camshaft, you may have to ease the cam tunnel to fit.
I would go for the 356 cam which is what the Super Flash used and would develop as much power as a plunger frame can handle, unless you are a thrill seeker.
Trev.