If you plan on going out long distances, consider a 20MOA rail
If not, any mount system will do... weaver bases, picatinny rail, etc.
on a 40mm bell, you might be able to get by with low rings (pending what rail you get). Otherwise mediums will clear.
Depends on your budget.... from baseline rings, to QD (quick disconnect). Don't skimp on the rings, get something quality (vortex, burris, leupold, etc).