Just go to your LGS.
Mine have uncle mikes swivel studs for $5.
I would definately drill a pilot hole. How big i'm not sure. Start with a 1/16'' and slowly step up the drill bits until its a real snug fit.
A tip, when twisting them in there, an allen wrench through the hole makes life a whoel lot easier
Its an easy process, at least the centerline of the plastic stock was visible. Idk about your wood one. Measure at least twice, drill only once!
581 Series 18.5'' Mini 14 Ranch Rifle SS
Henry .22 S/L/LR Frontier