I replaced my running lights on our boat with LED's several years ago and I surely couldn't tell any difference. I don't think the Coast Guard is going to board me to inspect for LED running light compliance.
I recently replaced all the cabin lights on the boat, and the interior 12 volt lights in our motorhome with LED's. Check out the parts section on eBay motors, they have a complete section on lights. I even found red festoon LED's for our dual-mode cabin lights there. I purchased them for a fraction of the cost they get at West Marine and the RV store, plus free shipping! For example, I replaced 6 1141 bulbs in the RV cabin for less than the price of a single 1141 LED bulb at Campers World.
Just remember, LED lights only work with the correct polarity.
Don