I am not sure what you mean,flanges versus grommets, without pictures. I used to wire trailers and I thought I was up on what was avialable. Anyhow, I think you are always better going with the original lights when possible.
I am about to start rewiring, and for now, tail and running lights. Would it better to go with lights with flanges rather than grommets - or does it make any differance?
Everybodys' opinion counts!!
We did a LoveBug with grommet lights , both running lights and tail lights,
It looked and worked great! One advantage is that all wiring plugs are inside the trailer. another is that you get a whole new light assembly when needed for a couple of bucks.
Another advantage is that they come with the ground wired into the plug leaving little chance for corrosion and easy wiring and or repair.