If you'd like the exact paint code that was originally used, I can tell you PPG 3116 single stage enamel was used on the older Cummins built crate engines.
It comes up in the computer as AMC Mandarin Orange. I asked but couldn't get them to do that exact shade in lower cost (like Delfleet) enamel anymore.
If you want it in single stage urethane, PPG can do it in Shopline at a reasonable cost.
I shot this one with PPG Shopline single stage, with Matrix black epoxy primer underneath.
If it looks thin, that's how I shoot them purposely.......I can't stand the super thick "dipped in plastic" look on anything I personally do.