I don't think you have to match the old color exactly, including the patina. Not sure if that's what Jefe was referring to anyway? My '68 has all new paint under the hood and mostly original paint (with all the usual blemishes) on the outside. Looks great and not out of line to have that new paint when you open the hood I don't think.
It would look nicer and still be appropriate. After all, there are still vehicles out there (including some Broncos) that have faded old paint on the outside, but the original paint under the hood still looks amazingly good for it's age.
Some EB's get the standard satin black treatment under the hood, and it actually can look pretty good. Lots of other vehicles came that way anyway, so it does not look completely out of place to some I'm sure. But I still think that body color looks better because that's how ours came from the factory.
I bet Duplicolor has their exact-match paint in a can of your color, so if it came down to it, three or four of the small cans might just do the trick.
You could always start off with one can, spray one part of the engine compartment, then paint it black after if you just didn't like how it was looking.
Paul