Vintage BMW Motorcycle Owners

Recently picked up a roller 1962 R27 with the engine out, stripped & partially reassembled. The seller noted that the engine case threads for one of the tappet guides was stripped. He obtained a spare case with the intent of building the engine into this spare, that was in 1992. My intent is to have the original case repaired and am looking for advise on locating a machine shop that has done this kind of repair or is highly qualified to make this repair. Any suggestions or previous experience are appreciated.

I am sure scottie sharpe could do it.
S

Are the threads totally stripped out or just the top few crossed threaded ?
Make a thread chasing tap if just a few are dinged up and screw it in from the bottom if there is room.
Probably no need to harden the tap.