What color should I choose?

I gotta agree with what cascius said, if it's going to be his car. Also this your car, not ours. Paint the engine bay black if you want. Many of us may not agree with that but it's how we personalize our cars to reflect what we like. Me personally, I'd paint the engine bay the same color of the car. I painted my 340 hemi orange in my 68 because that's what I liked. Bare aluminum intake is ok by me. If you wanted to make it look like a 273, put the 273 valve covers on it. Either in black crinkle finish or engine color.
Just me and what I'd do and to give you ideas.

Paul