They sold 40% and 70% both FAC and century had them when they were separate companys a few years back
I have got two 70% sitting here ready to go, I am doing mine by hand. I was going to do this with others, but I have lost touch with them
if done without a milling machines I will have to use taps, I got quotes the other day its over $100.00 for the taps but I will use them twice! all the interior cuts will be done with a mounted dremel and /or drill press, hand files, I am in no hurry
the front end is the problem, the thread timing by hand will be fun, but with shoulders I should do ok.
heat treatment I have given this a lot of thought and read every thread out there, this has been done before so I can do it. only I am going to use a blacksmith to do the heat treatment by temp/color
I have downloaded all past posts on doing these 70% and I will be working from these threads were posted by others. Roderus has several posts/threads going way back in the archives on these builds. got to do the research
since you asked for thoughts