I have read a few posts on this and other forums from shooters wanting to mount scopes on their C&R rifles. It is difficult to mount scopes on a milsurp rifle, even using a scout mount type scope, because of the bolt handle or bolt location.
Aperture sights are a very good alternative, but were not offered originally on many rifles.
Mojo sights look like a very good alternative to scopes. UI intend to buy one for my M39 and probably my K31, and leave my 98k and M96 as is.
The price is good and I haven't heard anything negative about them. Aperture sights are almost as accurate as a scope, but without the magnification. Aperture sights are almost as fast as open sights in brush.
It's worth thinking about if the open, original sights are a problem. I am 45 and the sights are becoming a problem for me. I also like the aperture sights on my M1 carbine.
The Mojo sight is a really well made sight. It gives you a nice sight picture as well.
The only thing I do not like is the fact that it is not realily adjustable for elevation. You need to use an allen wrench to do this. For 90% of shooters out there, that should be no problem though.
Williams (I think it is Williams, slim chance it might be Lyman) makes a rear peep sight for 98 type mausers. You have to drill and tap two holes but they are at the right rear of the reciever just in front of the safety. Rather easy to do and makes accurate shooting quite a bit easier.
I have done one this way and like it very much.