Hi Scott
Was the one you missed the center one? Glad you got it off anyway. I've been amazed over the years how ugly cylinders can look with rust and how much cleans up.
Now a couple of things to check take a look at
http://canadianmilitarypattern.com/H...May%20Work.htm some of my pictures of working on my HUP engine, first check the valve seats for cracks.
It may be worth having the whole engine magnifluxed before you do any machine work. Still going to cost you to have it hot dipped and cleaned along with the magnifluxing but it is far better to find the cracks before you start spending money on machine work.
Concerning the pistons, remember that CMPs like yours and mine use domed pistons and domed pistons will not work on the head designed for flat topped pistons. The domed heads will work with flat topped pistons but you loose a lot of compression/power. Flattop vs Domed heads:
When I rebuilt my HUP engine the head had numerous cracks in the valve seats and as the only NOS head I could get was flat topped, when they bored the cylinders went over to flat top pistons.
Cheers Phil
PS all the photos and more are over on my website, still need to do some work on the Overhaul pages and index the page better.