You could check on this place.
https://wagamonbrothers.com I have not used them but I know they do flat heads. I stop there for something and they had a couple on the floor. I used this shop in New Brighton MN when I rebuilt my willys 134 flathead. They did a great job on the block and machine work. Very friendly. I think it is called Metro Engine service (52 1st St SE, New Brighton, MN 55112 +16516364008. I know it is in the same building. They changed there name a couple years ago. They are very busy. But have done a lot of flatty's.