According to Ruger:A 3/8" rimfire scope base is machined into the receiver, which is also drilled and tapped for Weaver® #12 bases (not included).
The rimfire base on mine was a couple grooves cut in the receiver that the rings that came with my $60 Simmons scope fit into. (Dovetail? You’ll see that in the Warne link) If you want a weaver or picatinny base:
http://warnescopemounts.com/ruger-am...imfire-mounts/
http://shopruger.com/American-Rimfir...uctinfo/87502/
http://www.diproductsinc.com/Detail.aspx?PROD=1039632
Etc.