Those stud holes are in the wrong place for my application and there's Cast Iron about halfway down. I've gotta bring them In towards the bore a couple mm, I forget how many. Studs are 6MM diameter.
Whole thing is around 50mm deep. But modding this and making an adapter plate for the intake is all I need to finally have a 'correct' cylinder for This engine:
I was thinking of using a straight shank 7MM drill bit, slow, with a steel jig plate half an inch thick guiding the bit and lots of cutting fluid.
Oh, and a BIG shout out to Doc, and everyone here. I got this job because I've sat here and read the ancient scrolls penned by cranky elders for sixteen years.