A lot of it might depend on what kind of headers and/or coatings you might have. I think headers would tend to run hotter than cast iron manifolds, but I really don't know. I've measured my 71 Vette with a stock 350 and headers at around 800-900 when I bring it back from driving it around, but it's pretty cramped in the engine bay, so I would expect a little less in an A body with more room around the engine. Ceramic coatings and paint would probably also mess with numbers some, but I really wouldn't know how much. I would think it might drop temps some (keep the heat in the exhaust, not on the pipes), I think I recall seeing most coatings claim to make the exhaust tubes run cooler, maybe 100 degrees or so?
