I see you are in McKinney. Plano Machine Shop, in Plano will do the work. They are located on 14th street (by the Dart rail tracks) in downtown Plano.
By the way. Are you looking for someone to just do the machine work. To machine the block and valve seat replacement and you do the knockdown and rebuild, or complete overhaul?
I've had them do some work for me. They did my king pins.
Otherwise, I believe Dallas Motors on Harry Hines will do a rebuild.
I have also heard there is a place in Fort Worth that specializes in our vintage motors. But don't know the name of the place.