Several ways to go. Eagle makes a polymer 'L' to replace the Ruger factory metal 'L' peep. Mine works very well. If you want a larger hole in the apendature, just get a drill bit to match, and drill the polymer peep larger.
In think Millitt makes a whole unit to replace the Ruger factory. Millitts all metal, like their pistol sights.
There may be more options, Ashly may make one.
In any case, the Eagle works find for a service rifle site. Note the Eagle is slightly oversized, and may require a bit of filing to fit, but once you have fitted it, it will NOT be loose, like the Ruger one.
If you want more adjustments, disassemble the sight, and get a drill, perferabley a fixed one, and drill 4 more holes in the drums so as to give you 8 holes to 'click' through, instead of 4.
I don't know about scopes, as the military mini-14, to me, is more of a battle carbine than a hunter. I plan on getting a Mini-30 and scoping it (it is ranch rifle style). Refit the gas block, and I bet I get 2 inch groups at 100 yards (I get that now with my 'Micro-14', as I call it).
Deaf