66 Engine Compartment Paint???

I'm not sure of the paint mix number for the underhood black (I think I've seen it mentioned on the Vintage Mustang Forum). That'd be the most "authentic" way to go - look that up and have a quart mixed. Eastwood Underhood Black is also popular.

Krylon Semi-Flat Black spray paint (#1613) was recommended for years as both easy to find and "close enough" for anything other than serious restorations, but Krylon recently moved that paint to its Industrial products line - it's no longer on the shelf at Wal-Mart and your local hardware store .

Another thing to consider before getting too worried about 100% correct is that even if it's perfectly correct, the first time you clean it with whatever you choose, the gloss rating will change instantly. Matte finishes collect dust like an old lady collects stray cats, and I've used everything from Formula 409, to various brands of spray detailer, to Armor All (low gloss) on matte finshed engine compartments and they all shine it up significantly.

I sprayed the bottom/engine compartment in Dupont 'stock' black base and Standox satin clear. It has the correct 'eggshell' color, and the advantage of being tough as nails.