formula needed

I'm workin' with a 400M engine, the block has been decked, and the heads got a shave. No spec on either one of those. The valve lift on this cam is .468, duration (@.050) is 206 degrees. I'd like to up grade from stock rocker arms (1.6/1) to full rollers. Ford motorsports only sells 1.73/1 units. Question: How much more valve lift am I gonna' see... enough to worry about VPC problems?

Your valve lift goes from 0.468 to 0.506.

(4.68*1.73)/1.60 = 0.506

I can't tell you about clearance. Since you have no spec on the head milling, the safest way is to measure it by pulling a head and using clay.