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I will soon attempt to have paint adhere to the newly chromed bumpers on my '37 120. I would really appreciate any suggestions as how best to prep the surface, and primer and paint to use. Thanks

I didn't do anything fancy - wipe the area with a mild solvent like isopropanol or acetone. Use an oil-based enamel. Has held up fine.

Also be sure to use a low adhesion masking tape. The first time I did my bumpers the masking tape I was using pulled the paint off in areas in a saw tooth look. The second time I painted I used a masking tape called "frogtape" which if I remember I purchased at Sherwin Williams. Removed it right after painting and then had a nice sharp line.

Sand the spots you're painting with a very light grit sandpaper. Marine coatings tend to require 220 grit for proper adhesion (and no sanding mark print-through!), so with automotive coatings I'd go with 400 grit or maybe higher. Mask off immediately around where you're painting; the masking tape will protect the part and keep the grit from harming the finish, so long as you aren't a gorilla about it.

Bob Villa did a writeup on painting chrome plated house fixtures that might be worth reading

Thanks for sharing your experience. I assume that the bumper inlay and guards on the '37 120C 4 dr. convertibles that came from the factory were painted black/red, I was surprised to see photos of some '37 120C's that were not painted. Were they painted a gloss black, etc. or satin?

I know from previous experience that it is difficult to get paint to stick to a chrome surface. The process I plan to follow is:
1.sand surface (220/320/400)
2.degrease/clean
3.tape
4.Prime with self-etching primer.
5.Paint with epoxy paint.
6.immediately/carefully remove tape.

I wouldn't sand. That'll permanently ruin the chrome surface. Listen to what "Kaz" said.

Make sure it's very clean, no wax, silicone, etc. I use prep-sol before paint.
I think self etch is bad as well. People have been using it wrong ever since it came out. You don't want acid trapped between the metal and paint - bad for the paint and adhesion. That's mainly use for aluminum to tooth the anodizing which neutralizes it.
You can use a little adhesion promoter spray, in place of the self etch, if you're worried. It's used for plastics where there no good penetration and shiny surface.

I wouldn't bother with the adhesion promoted designed for plastics. The mechanism by which it works(basically damaging a thin surface layer to increase its polarity) is not applicable to chrome.

Thanks for the advice. I have since read about self-etching primers and you are right that it is not always the right primer to use.

Self -etching primers and plastic adhesion promoter primers are two different things. The former is for bare steel, the latter for (primarily) thermoplastic olefins like modern bumper fascia.