1" precision matched rings, these are he good ones, serialized, made in USA. I believe Seekins makes these for Vortex.
Used very briefly on a 300 blk bolt gun, so they've seen very little recoil.
Also have a Remington short action Leupold Mark 4 20 MOA I can add for pretty cheap. That would be be a darn solid foundation to put on your old Rem 700 .243