update:
Research and advice from my son-in-law shows that two replica scopes and mounts are readily available for 91/30.
Both the Hex and round receivers apparently can use the PU scope and mount from
http://www.accumounts.com/
They have the entire PU setup including scope, mount, screws, drill, and tap for about $200 and it will fit either round or hex receivers, or so they say.
For the PE you need to find a scope (Coles Dist. has a complete setup for a round receiver or just the PE scope, all very expensive). The PE mount (PE over the receiver vs. on the side of the receiver for the PU) for the hex or round are available seperately from the above Accumounts but no PE scope. The best you could do is $300 for the PE scope only from Cole's and $130 for the Hex or round PE mounts (over the receiver).
Since the price differential is so great and Mosin-Nagnat's are NOT my favorite rifle, I'll go for the cheaper PU setup even though the stock has to be relieved for clearance. The scope setup will be worth more than the rifle!!! My son-in-laws PU setup shoots really well hitting ram sized steel targets at 500+ yds almost every time. And his is a shorter carbine!
LDBennett