you would need a machine shop, blue prints, and a class 2 manufacturing license to make a receiver for an MG-42.... or you could do it without the license, as long as you don't mind getting a 'go directly to jail, do not pass go' card in the process.... 😀
Dave
Edit: Even if you had the license, it would be a post 1986 MG, which makes it not worth the money you would put into it....