Here is a copy of the information that I send out when I get asked about this subject. The tips I give are from doing this for many years to replicate a correct restoration.
The Indy Valve Cover and Air Cleaner paint codes:
For quality Automotive Paint, It is a Chrysler color, CA1 Radiant Silver
Chrysler Code DT 9049
PPG Code 3556
Duplicolor makes a spray can version in either codes:
DSCC 338 Radiant Silver
DSGM 340 Silver Metallic
Spray can paint is close in color and texture, but leaves a little to be desired in a perfect replication and the spray can paint will not last as long.
Some notes for correct duplication:
1) Spray the silver over black primer or paint as the originals were dipped in black paint before being sprayed silver. The factory just grabbed standard iron duke valve covers and air cleaners out of the production parts bin and sprayed them silver.
2) The original paint was enamel, so if spraying urethane based single staged paint with a gun, reduce the gun pressure and increase the spray distance and spray pattern width to duplicate correct texture. And spray the parts like you have been standing on an assembly line all day and it is almost five o'clock with a pretty girl and free beer waiting for you at the bar after work. Thin spots, runs, sags and dirt particles in the paint are normal.
3) Paul KcKibben of Fiero Sails makes an excellent duplicate graphics kit in decal form or a reverse image mask that you can use to replicate the original screen printed graphics with an airbrush. http://www.fierosails.com/decal.html