Well, if the light fixtures are like mine, they were chromed. If pitted, no amount of polishing will get rid of the pits without removing all of the chrome, at which point you just have stamped steel which will need to be painted or rechromed.
JoeK '61 16' Airflyte
Vintage Trailers: a common dream for uncommon people
My light fixtures were pretty bad. One had water filling up the globe from a leak in the roof. Very rusty and rough feeling. I used CLR cleaner (Calcium Lime Rust) to clean off some of the rust, then used Diamond Brite aluminum polish (got it in the truck tool box section at Lowes). They came out great. I decided to clear coat them to try and prevent future rusting. I rubbed them down with lacquer thinner and clear coated with a "water" clear lacquer. Time will tell if the clear coat prevents the rust. The Diamond Brite polish is the best metal polish I've ever used / works great on brass too.
Forgot to mention: On some of my really pitted stuff, I used the grey color 3M scotch bright pads with the liquid metal polish (mentioned above). Smoothed and polished well. The grey 3M pads are not as course as the green pads. Pads at Lowe,s too.
Had the same problem on the bargman L-66 door handle the grab handle next to the door and the license plate lamp. We filled the pits with body filler, sanded and then sprayed with sandable primer/filler before painting with a silver/gray automotive paint.