helgesen E-tool??? Help!

I am getting ready to go at the 302 casting heads with the old grinder after having practiced for about 8 hours on my original '74 318 heads. I keep reading about how the 302 heads have less material around the pushrod and to be very careful. The articles I have read talk about using a Helgesen E-tool to determine how much metal you have before cutting into the pushrod hole. I have looked everywhere and can't find this tool. Does anybody know where to get one? Here is the link to the article that references it and shows a picture. Thanks
Author: admin