how good of a finish will that give you? if not damn good then leave as is...
i didn't paint under hood of our dart because the entire car is original paint and it would look out of place. hell i was temptet to make the new engine look used and abused but just couldn't bring myself to do it..
if that demon was mine and the engine was out i'd definatley paint the engine bay. it would have to be done right though and look about perfect when done.. now if the roof and quarters weren't done i woudln't bother..