I take it that the rifle currently has a "blind magazine" meaning no floor plate. If that's the case, I'd definately seek the advise of a good gunsmith before trying to adapt it myself. The reason I say this is the design of the stock. If you cut the bottom of your stock out, and it's not made for that purpose, you may weaken the stock enough that it flexes more than it should. A solid bottom stock has it's own reenforcement by virtue of the wood or fiberglass where the floor plate would go. Stocks with floor plates (some I've seen) have extra material to help reenforce itself in that area. A stock that flexes too much will rarely be a good base for an accurate rifle.

Just my thoughts on it.

If the stock has sufficient material to allow the modification, you should be able to order parts from Savage.