I have mine coated, did it myself using a Eastwood home unit and old oven. My dads engine has everything powered except the block and heads (Pontiac V8) and has held up well for a many years. Engines only get to 200 degrees or so, powder cures at 400, so it holds up just fine.
Both your 250 and your dads v8 have manifolds that do not connect to each other. I would be concerned about the heat transference through the metal bolted together. Also, exhaust manifolds get a hell of a lot hotter than 200 F degrees.
That would be my concern.
Jeff
