There's a guy not far from you that was making them, he's a member here, he's down close to Savannah, username something like "69 340 6 pack".... (Maybe delete spaces? It's been a while since I've talked to him/ not sure on the name)
Good guy. I've bought 80s D150 parts from him before.
(Was my once in a lifetime trip to GA haha)
I think he has a water jet or something. He does those, and the underneath block off plates when not using the stock exhaust manifold.