I dont know off hand the exact arrangement of the ring gear and diff on a Savage, but If its a bevel gear anything like the Losi LST's, the thickness of the gasket can effect the pinion contact with the ring gear. You might have to shim the diff differently.

I make my own gaskets for all sorts of engine parts. That is, if they used paper gaskets in the first place. If there were O-rings, I'll retain O-rings and use Ultra Copper RTV. Paper gaskets always get a thin film of UC RTV on both sides of the paper and assemble parts immediately. The best paper I've found for making into gaskets is 50-70lb white cardstock. About the same thickness as Index cards. When I make "ghetto gaskets", I cheat. Stick the cardstock in the AIO printer, and stick the part I need a gasket for on the scanner bed with white paper covering the rest of the glass. Gives me a perfect image of the near-exact size of the gasket needed.

I need to get a hole puncher that makes teeny holes instead of the standard size hole puncher for the screw holes. I need to make some backplate gaskets for a couple airplane engines I have and cutting screw holes with an X-Acto knife takes forever.