Thanks for all the replies. I am going to go ahead and get it coated, whether that fixes the alternator problem I have been having or not, it looks good and will still reduce under the hood heat.
Don't count on on ceramic coating to reduce underhood heat much at all. If you chose a light color it would reduce the radiation component of the total heat released from the hot manifold. The bulk of the heat is released by convection (probably 95%), so you MIGHT get a 5% reduction in under hood temperature, but I doubt it.
