Cal -
Get the grease off with something like citrus cleaner first, then bleach will work - unless the oil/dirt/crud has gotten too deep into the plastic.
However, you can get some brand spanking new dead-on repro targe top latchs cups (the bigger 2) from either 914Ribber/Mikey914/Mark W. or AutoAtlanta or GPR, & maybe Stoddard's Classics in OH &/or Einmalig &/or SMC in SoCal.
PS - if the other is the rear trunk floor plug, then Mark W. may be making them too - or you can ask if he can.
Tom
///////