Re: 30mm rings with + 20 MOA for Ruger 77/22
Weigand Combat makes a nice (flat, not 20MOA) weaver or picatinny rail for the 77/22 that goes on easy. Not sure why you would need a 20moa base to shoot yards though.
Ken Farrell has something for the Ruger No.1 (which has a flat base, and shares same height rings like the 77/22) but not sure if the No.1 and 77/22 are exactly the same, and requires drill and tapg - would email them on that one.