Welcome! Some of this is covered in the FAQs sticky, but I'd have to go with a blued SB2 rifle frame made 2000 or later since H&R has made improvements in heat treatment and such over the years, they won't fit any high pressure barrels to frames made prior to 2000, nor will they fit rifle barrels to SB2 10ga shotgun frames. Matte nickle and all stainless frames are made to the same standards, the only stainless frames ever made came on 45-70 and 444 Marlin Ultra hunters, any other "stainless" rifles have matte nickle frames. All SB2 frames, rifle or shotgun, are heat treated investment cast alloy steel. The SB2 10ga frame is weaker due to the thinner frame rails, it's also not really suitable for high pressure rifle cartridges due to the large shotgun firing pin.
Tim