You should be good. The 220 SMK is a large bullet and not super sensitive to jump. I wouldn't worry so much about the specs of the mod 1 and just work up the load for your rifle. Make the COL as long as your mag will allow to leave room in the case and help drop pressure just a hair. Using a large rifle primer instead of a magnum will help keep pressure in check too. The Mk 248 mod 0 stuff I shot up a couple years ago was loaded in Winchester brass. WCC head stamp "Western Cartridge Company". The load was hard on brass just like I'm sure the mod 1 load is.
I'll dig around and see if I have any of that stuff left. I included a lot of it when I sold my .300 WM.