Claude is right.
But you can clean it up quiet nicely if you are supper detail orientated. First it needs to be clean. Start by removing as much as possible, coil pack, wiper motor, ground wires, wiper actuation rods, cowl weather strip, maybe the lower windshield trim, or anything else you can depending on how far you want to go.
Then use aluminum foil to tightly wrap components, masking tape, old towels to shove into spaces, newspaper, you know the deal. Use semi gloss black. it will loose some of its sheen over time. Don't use gloss unless you want it to look absolutely ridiculous next to the rest of the shit that is 30 years old. By the way......you might as well take every other accessory of the engine and clean detail and paint it as well.
Or take the whole car apart and clean everything with a q-tip and toothbrush and then paint it.
What's the difference? You may not be going anywhere for a while. I know I'm not.
I originally did the top part of firewall while engine was in with the Technic like Twin Turbo suggested then when the motor was out I did the rest. I would recommend using Satin black it has a little less sheen than semi-gloss.I was looking at my engine firewall and it looks kind of ratty. Anyone try to paint it with the engine in. Possibly spraybomb it.