Can anybody clarify the black engine compartment paint originally on the 69 H/O I've seen it Gloss seen it Semi Gloss & have seen it Satin BLACK this is the front support rails the Radiator bracket and Top Plate and in general all black covering fenders cowl/firewall
Basically what COME FROM THE FACTORY
Thanks
Alsmith787

 

There isn't just one sheen in the engine bay from the factory. Firewall cowl area is different from the frame, different from the core support, rad top plate etc.
Each of these components got painted separate. If they came from a vendor painted they had a spec they needed to hit but it wont be uniform throughout. Several Olds line workers can attest to this. It was the same throughout the industry then. The NCRS Vette guys have "vetted" this out years ago.

If you are looking for 100% show correct contact the H/O club guys who have unrestored cars for general guidance.
If exact replication is not a concern and you want a nice presentable uniform paint, several vendors offer "engine bay" paint. Its a semi, satin, or reduced gloss paint not sure what the exact formula is. Eastwood has a few different sheens.