I notched the pistons in my old 4.6 motor with 2 used valves that I used a cutting wheel to notch the edges to put 'teeth' all the way around. Then hacked up 2 screw drivers and welded them to the ends of the velve stems. Then using the head as a template stick the stemsup through the holes and attach a drill to the valve stem. Doesnt take long to chew into the piston. Dont need to remove much material. 4.6 motors are notorious for high lift cams smacking the crown of the piston, thats why I did mine. Funny thing is that I never swapped more than PI cams back on to them. SBF motors will hit towards the center of the pistons. Allow enough clearance in case you get some valve float to CYA. the valves are usually between $7 - $9 each for stock valves from the parts store. Or check a few garages out and see if they have any old 2.02 valves they were tossing out.

Oh and I bevel the edges of the depression in the piston with a dremel and a round sanding bit after I get the depth I'm after.

Its really easy to do.

Also,.. IIRC Shawn and John over at All American have or had the tool to notch pistons with.

Hurst