I milled my head as much as possible and raised compression to about 9.5:1, and didn't have any piston to valve clearance issues. But that was with a stock cam.
When you upgrade the cam, you really should check.

And for the person asking if you were taking two steps forward and one step back by milling the head, no you aren't.
It's because when you measure displacement of the engine, it is the volume that the piston displaces, determined by the sweep of the piston. No, it's more like taking 3 steps forward and no steps back.

On the formula, I knew how to calculate it, but didn't know the bore and stroke of a 235. But thank you.

52 GMC 3/4 ton pickup
68 Big Block Vette
68 455 Firebird