kevin.303 - I agree with MG on the Boyd's stock. It is inexpensive but it is not the tightest fitting stock around. However, that being said, that is what bedding compound is for.
I have a Richards Micro-fit stock and it is a beauty. But the dang thing took 6 months to get and was pretty expensive. I went with Boyd's for those two reasons for my next Mauser stock.
I don't recall, right off the bat, what the B-Square mount looks like on the No 4's but I have one of those 'no-gunsmithing' mounts from someone that fits into the rear sight base and over the charging bridge. It sits nice and low and works very well for me. It is secured inside the charging bridge by a double set of set screws but you may have to dimple the (shallow pocket or hole) inside of the charging bridge first with a small drill bit where the screw would seat to seat it positively. HTH. Mikey.