The B-Square will mount a scope to the Mini-14 well, and is commonly available.
The Ranch Rifle has rings included, but also has the receiver machined to accept those rings, no separate mount needed.
The Ranch Rifle has the ejector redesigned to eject the brass more to the side. The regular Mini-14 ejects more upwardly, at such an angle as to usually strike the windage turret of your scope.
A common trick, rotate the scope 90 degrees to the left, and now the elevation turret becomes your windage adjustment, and vice versa. The ejected brass will miss the scope.
The Choate Pistol Grip Stock (which is a non-folder, a folder being illegal on a post-ban gun) will greatly improve accuracy of the Mini-14. This stock fits the rifle very tightly. The loose wood OEM stock is the cause of much of the Mini's accuracy problems. Unless you want to spend a lot of money having a heavy barrel put on, about the limit of what you can get will be 1.5"-2" with the Choat stock and good scope. This is fine for a lightweight, inexpensive carbine, which is all the Mini-14 was ever intended to be.
Do not get a scope with objective larger than 40mm, or you will need very high rings to mount it. A low power, 2.5x to 4x fixed power scope, will do well on the Mini.
I would point out that the AR-15 A1, with its light barrel, was at best, a 3MOA rifle.
Precision Mag, aka PMI, is your best bet for a large capacity mag. Their 20, 30, and 40 round mags function flawlessly. I prefer the 30's, as they fit the same webgear as my M16 USGI mags.
I made a neat cheekpiece from foam water pipe insulation, some tie-wraps, and a piece of black leather grain vinyl, strapped to the buttstock of the Choate stock.