It is true you should check for valve clearance after having the head machined, but on this type of engine, there should be no need to worry.
Possibly, but he does have an 848 head on a 261, with a somewhat modified camshaft. Once the stuck valve is repaired, I believe a check with modeling clay or some other method of measuring piston/valve clearance would be the prudent thing to do during reassembly. I usually bolt up the head without a gasket installed, and if there's even a little clearance that way, the thickness of the head gasket is enough of a buffer to assure safe operation.
On the round track engines with radical cam profiles and high RPM, we used .060" clearance as a bare minimum. One engine we ran had such a radical cam profile that the closest piston/valve point came 20 degrees AFTER TDC. The intake valve was outrunning the piston for the first 20 degrees of the intake stroke!
Jerry
