Thicker thread used on coats and for fastening buttons works well and looks a wee bit better IMO since it's a little thicker. Thats what I used on the Super Bee in the previous pics and the Surf Woody below. Problem is the limited colors.
You can also get craft wire that works well too for forming brake lines, throttle lines, fuel lines, etc. I got one that came in a 9 pack, all different colors at AJ Wright (A craft store.)
This is a '67 Mercury comet that I experimented with. First time I cut open the doors and trunk. Made a fake Hounds Tooth trunk mat with a piece of paper and my kids colored pencils.
Where's bentpushrods? I bet he has tons of cool hinters!