Do you have a valve spring compressor?
You need to get some "checking springs" and install them on a intake and exhaust valves.
We all can guess at how much lift you can use but it's only a GUESS!
and when you guess or ASSuME, The Eng can go BOOOM!
Checking spring and a dial indicator will answer retainer to head and Valve to Piston.
My 340 was a little shy on the valve to piston clearance(.474 lift) do to the valve relief having a ledge. Did a little trimming and i could get .500 lift(where the retainer hit the valve!) With a .474 lift cam, it was good enough.
checking spring are not that much money, well worth the investment!!!!!