all trucks came with a gray interior, except Cameos, where interiors were keyed to exterior - I know of no modern paint codes for the interior colors, which originally were Duco or Dulux Granite Gray, Marble Gray and Charcoal ... the dash top is the only flattened area, and you should be able to get a flattening agent for whatever line of paint you use
the tag would indicate body color/pattern [like 2 tone], not interior, and the level of trim, such as deluxe interior [chrome bits, better seat] ... the assembly manual and accessories book show RPOs and options .... original build info is almost non-existant for 50's trucks .... also lots of info may be found at
Keiths manual siteBill