Not too many companies made side-mount scope bases for the Springfield - even when it was popular for sporterizing projects.
Mine had a Griffin & Howe double-lever side mount - but, for the life of me, I can't recall how many screws anchored it, those many years ago.
IIRC, the Williams QC Convertible Side Mount base has always used three screw, ILO the four on your rifle; and although Weaver made them, I think they used three screws also.
I would contact G&H with all your rifle's screw hole spacing measurements, and the screw sizes.
If they no longer currently make the base, perhaps they will custom drill a blank base to your measurements.
http://www.griffinhowe.com/mountsandpads.cfm.