The main names are SSS (Fred Moreo), Stockade Gun Stocks (Kevin Rayhill), and Savage Gunsmithing (Scott Null). Lots of other good smith's out there that will work on Savage's though that should be able to accommodate your needs.

Receiver threads probably just need cleaned and possibly chased with a tap. 4-D rents the tap if you'd be interested in doing it yourself.

https://4drentals.com/product/savage...tandard-shank/