1975 So Cal "installed Smog Thing"

I remember working at the Plymouth dealer in '72... the emission cars had plastic caps on the idle screws... we got a notice from the Feds that we could not take any car in trade unless it had the factory caps on the idle screws. Of course the sales dept. DID take them in after convincing the customers that there trades were only worth half price without those caps. Then I got them and had to install new caps!