Buttstocks are fine, you may just have to buy a different bolt OR add a bunch of washers if you're going from adult to youth buttstock like I did for my little ones.
On the otherhand, the forend stocks weren't as interchangeable as I was hoping they would be. YMMV, because some people have had them drop in fine, but the majority I've read have done a little tweaking.
I have only three newer frames(Ilion produced) and they can swap between each others H&R stocks(both forend and butt) fine, one forend just a little tighter than the two. But the two NEF synthetic forend stocks(choate produced) I bought online need some rasping and/or sanding at the spacer to fit right which I don't want to deal with right now, maybe in the summer. Seems easy enough.
Hope that helps.
