A 73 Dart is still a MOPAR and deserves a body color engine bay. To say that it will never be worth much isn't really accurate. Have you checked the prices of nice ones on ebay lately? Yes, the values have risen. Maybe you dont care about the factory correct aspect of car restoration. It is your car, but I am another one who thinks that black is hack. Fords and GM cars did the black engine bays. The bedliner coatings are worse. "Black is good for touch ups". THAT is a crock as well. Do a decent prep and paint and the finish will be more resistant to scratching and flaking off. Personally, I can only understand the alternative paint ideas if your car is a rusty old turd with a slant sick running on 3 holes, belching oil smoke from the 1 7/8 single exhaust pipe. That doesn't sound like you.