I can tell you that is a shortage of manifolds in the southeast. Just got a set in for a customer's boat and they came out of Arkansas. My distributors in south Fl isn't doing any better. Everyone is going into the winter and depleting their summer stock.
You can Contact LKQ (Like Kind Quality) a major dis mantel center here in Crystal River they MAY have what your looking for,they ship parts all over USA (Big Place ) they have over 100 workers out in yard ,install tranny/used motor,all with Two year warranty ,
Yes I over looked fact these were for a Boat engine to late as I had gone to play golf, then said Oh Shyt that was not smart , sorry Capt owing to shallow water and such not that many inboards this area at all. Good Luck in search