Roller Block: Pushrods Rubbing Against Head
Do what you were thinking and go to HF for there die grinder and grab some carbide bits and run it up and down untilit clears. Be careful not to go overboard. I had to do this to several heads when going to a roller cam because of the shorter pushrod length and the taller lifters that aggravate the angle of the pushrods into the head. I used tan colored masking tape and wrapped the pushrod to see if it would rub at all and ground away until the tape didn't get touched.
This sucks. You'll need to disasemble the head in the end to keep things clean and clear of all the bits and dust.