LOL.."Correct" Engine Color is always a hot topic.
Any original 235 truck engine or parts I have ever seen are Dark Gray. The New Ford Gray is way lighter than any Chevy I've come across...
Hirsch and The Filling Station both offer a Chevy Six Gray that are really close when compared to an actual part, and what I've used recently.
Those brands are kind of expensive though, and they have to be ordered and shipped and all, so that said, Next time I do a Chevy six, (or 283) I'm going to paint it with Industrial Engine Gray Engine Enamel which is just a Dark Gray paint, is Really close to original too and I'll betcha' what Chevy used back in the day...