Two recommendations, both a ways from you:
1. Mark Moriarity of Warsaw NY. 40 years experience in building flatheads. Very low key and easy to work with. One advantage is he has a TON of good spare parts, so if you happen to need something a little out of the ordinary he's gonna have it. Prices are right on the mark for today's costs; not a bargain but no overcharging either. All he does is Flatheads 100% of the time for his living.
2. Walt Dupont of Gardiner ME. Another builder with a long history on Flatheads. Did 8 or 9 engines last year. Has a background in stock car racing, so is meticulous to detail and especially cleanliness. I don't have experience with his pricing. He has access to a shake and bake process that leaves the block looking like a brand new casting.
I know there are others and don't mean to slight anybody by not mentioning them, but I've had experience with the two above.
In my judgement, (many mistakes and hard knocks) I've learned it's better to deal with a specialist such as these two than to try and school your local machinist in the ways of a flathead.
Just my 2c. Good luck in your project
Henry