TSP is working on the PRC LS6 S1 heads (w/ stock valves) milled .030 w/ MS4, though I've got slight valve reliefs. (1.5cc reliefs in the pistons).

...but Trevor told me the cam would clear flat tops w/ stock heads.

 

Yes, the MS4 will clear stock heads and PRC stage 1 heads with no clearance issues. If you go to the Stage 2, that when you have issues. Do the install yourself and check all your clearances. Its for your own peace of mind and saving money....money for more mods