The difference between the Ruger mkI and mkII are how the slide is held open. On the mkI when you pull the slide back you then flip the safety up. On the mkII, the have a safety and a slide lock.
All the replacement mags. I have found are 10 rnds. Some say they will fit both guns, I amgoing to order a couple this week and if they dont fit, then I guess I'll just have to go out and buy one of them mkII with the six inch heavy barrel, in stainless?? HAHAHAHA !!!!!!!!
Thanks for the help guys.