It SHOULD fit as is. Almost all, if not all, H&R stocks and forearms are made the same and interchange with no problems. The buttstock will fit for sure. The only problem you might have is the barrel might be a bit snug in the forearm. If that happens, and I doubt it, that is easily solved by sanding (opening) the channel in the forearm a bit with a dowel or broomstick handle of the correct diameter wrapped with sandpaper.
I'm not a betting man but I'd put money on it fitting the first time out with well above a 99+% chance...go for it with NO worries.
I have a thumbhole stock set with matching forearm on a .17HMR with a heavy barrel (I think they all are that way) and it fits fine....<><....