Clarence Lee does them for glow engines. He likely could do them for a gasser. Or maybe just a well equipped auto engine rebuild shop. A friend blew out all four plugs from his Mazda GLC and had them fixed with Helicoils. If the plug was a 10mm, maybe the head could just be drilled and retapped for a 14mm plug, or a 14mm to 10mm plug adapter could be used.

Sincerely,

richard