Helgenson E tool

Does anyone know the details about the Helgenson E tool to measure the pushrod pinch wall thickness for cylinder heads?? It looks like finding this tool is darn near impossible. Looking to buy or make something similar and I also posted in the wanted ad section but I am curious what everyone else is doing when porting?

I am porting a set of r/t cylinder heads and was smoothing out the pushrod bulge but then noticed an imperfection in the casting where the pinch is slightly thinner. Little nervous it might have been me that caused a hair too much to come off. Any help or advice is appreciated Thanks!!