These Heater Box Nuts Are Driving Me Nuts

[71ChallengerSE]

I am looking for new heater box nuts for a 71-72 plymouth with A/C but all the replacement nuts with the spinning washer I keep finding are phosphate. I believe the finish is supposed to be a zinc or yellow zinc. Also I believe they would be the same for non air cars as well. They are a 1/4-20 thread size with a 7/8 OD washer and a 7/16 hex.

 

[red 69 runner]

try here
http://www.megapartsusa.com/