Not to be a bust, but a strictly "mopar machinist" to me wouldn't be a good machinist. Midway engine builders in Salinas, Ca. are great with a great reputation. They're an all around machine shop that know their ****.
My dad had the same issue on his 383, came out to be a broken contact on the distributor rotor. Engine was getting enough spark to turn on and idle, but under load, it would die. Same thing with my 318, 6 months ago.