If you remove the rear sight assembly on a 91/30, you'll find there's a 3/8" dovetail rail milled right on top of the barrel. This will readily accept 3/8" .22/airgun type scope mounts, the best seems to be made by Leapers.
http://www.opticsplanet.net/leapers...set-optimum-profile-mount-rgpmofs38-25h4.html Combine this with a long eye relief scout scope, and you're set.
To remove the rear sight, you'll have to drive out two pins, and the sight base is usually lightly soldered on. A little heat from a propane torch and some gentle tapping will drive it off. For LOTS of info on scoping 91/30's, go to
www.gunandgame.com and search through the Mosin Nagant forum. There's several very long threads there about this, covering just about every kind of mount you can think of. With a LER scope, the bent bolt handle isn't necessary, as the scope will mount far enough forward to not be a problem.
Hex receiver rifles are generally considered more collectable, and they're pre-war so the machining and finish is usually better (war year Mosins, especially late-war, can be pretty roughly machined). No real advantage to the hex receiver, just a higher cool factor. My 91/30 is a 1938 Tula, a very nice one for the $69.95 I paid for it at Big 5 Sporting Goods.