I've mounted several scopes on M23's and was about to do one today! I use one of the Brownell's Universal Dove Tail bases and drill holes in the base to correspond with the two holes on top of the action. I put a scope on my .22 Hornet and am putting one on my .32-20. I then install a vintage scope. These rounds don't kick hard enough so the dove tail holds just fine. The small hole is, I believe, 8x40 and the bigger one a #10, not sure of the thread size!
BROWNELLS DOVETAIL SCOPE BASE STOCK

Brownell's - blank dovetail scope base stock 1", VINTAGE, NEW, NOS, .22 | eBay This is the one I use.

Try E bay for your parts. savage model 23 parts for sale | eBay