So, what engine colors were available during the period your build is suppose to represent? Distressed leather, and battleship gray make it look 50s ish, I probably would have to go with the orange, and loose the chrome stuff. If you really want to keep all the chrome on the engine, probably a dark red block & heads might look OK. 60s Ford blue would be different. Gene
Confuse em all with Chrysler 318 red....nice contrast....also the name begins with Ch...just like Chevrolet
I’m going a little less flashy, Ford truck gray from the 80’s. It will be lighter than your body color, so it will contrast nicely yet not stick out loudly.
Update for anyone who cares, and for those of you who do not, oh well... Changed up my mind on exterior color, going with a more 'traditonal' vibe: Washington Blue with 56' Chevrolet red engine. Probably an oxblood interior close to the engine color. Maybe some black fenders instead of a hiboy. Heavy chop, give it that sinister look.
I know you're asking about engine color, but I question your choice of going with brown interior/w gray exterior. It's like wearing a brown shirt with a light-gray suit.
The most important consideration is the exterior color. I wouldn't think about anything else until that's settled. Once you think you have selected an exterior color, look for cars of that color, preferably similar to yours, keeping in mind that photos might not adequately depict the actual color. If possible, contact owner(s) and ask if the color shown in photos is accurate. After finalizing exterior color, concentrate on the interior color. Engine color should be the easiest to decide.