If you are doing the truck as original or just want it to look "correct" Chassis black is the only choice.
If you are doing it custom/resto mod, or just to make yourself happy, paint it any color you like.
The 48 2 ton has all chocolate brown frame and suspension.
A personal comment, avoid gloss black. In my opinion nothing says amateur restoration like a gloss black frame. I'm sure that will start some comments.
