Tools & Fabrication - Flycutting Tool ???

I need to flycut my pistons and I am running trickflow 220 heads. I should be able to still cut with a GM head right ? Does anyone rent the flycutting tool with a mock up head ? or should I buy one of the isky or lyndy tools ?

there is a writeup on here that shows how to flycut with the head in place, in car. you basically take a used valve and adhere sandpaper to it to do it..

I think chrss1313 or sombitch rents thats.

I ordered the flycutting tool from Lindy. I need to use my trickflow head to get the proper position of the cut due to the different valve angle.