If you're building it replica stock, go to the Wal-Mart (or whatever) automotive section and pick up some 1:1 engine paint in Ford blue, Chevy orange, etc. I've used it for years on kits and have had no problems with it harming the plastic.
If it's going to be a hot rod or custom, paint it whatever color you like. Testors Metalizers are great for doing aluminum intakes, cast iron exhaust manifolds. etc.
Try looking on eBay for the 1:1 car you are building. Sellers usually include lots of pics of the vehicle they are selling. Good luck!
"Trust no one; even those people you know and trust." - Jack S. Margolis