Doesn't the notch in the piston point to the front of the truck? If so, the nick in the piston looks too close to the centerline of the pistion to be the edge of the valve, (or you have some really small valves.)
Does the head or block have any numbers stamped on them? The shop that decked my 2F head stamped an "050" on it to indicate to future generations that it had been shaved 0.050".
'03 KTM 450EXC
"If you know what you're doing, then you aren't learning anything." - A. Lincoln