I have a Winchester 75 Sporter some dimwit drilled extra holes in the receiver before I got it. I got a great deal on it, so I picked up some Leupold gunsmith bases, shaped them to fit the receiver on my mill and then took some careful measurements and drilled/countersunk them to fit the existing screw holes and line up properly with the barrel centerline. Looks like a factory job and works great. If I were to do it again, I would do the same thing or get a long picatinny rail and drill/countersink to match the screw holes.

Bob

Never underestimate your ability to overestimate your ability.