A well built, one piece base with 20MOA, or so, built into it would definitely be my recommendation. Badger Ord makes a great one, as does TPS Products.
Some scope manufacturers like IOR Valdada also sell a one piece unit with their scopes that have built in MOA.
As for rings, I like the Badger Ord and TPS precision again. LaRue Tactical makes scope rings that have quick release on them, which leaves the rail on the weapon. I am not a big fan of quick release anything on my boltguns, but that is a personal choice.
As for optics, Leupold is a great product and they have excellent customer service. Any of the serious big name makers ( IOR Valdada, S & B, Zeiss ) are probably producing a scope that is 10% or 20% better, but at 50% or more of the price.
I would say fully 65% to 75% of all the boltguns that leave the shop as custom builds have Leupold on them when they leave by owner choice. We have plenty of other people who have guns built and want NightForce, or something crazy for a specific purpose, like Benchrest, but they aren't as common.
Good luck with the purchase.