Replaced a couple burnt out fluorescent tubes on my Gold Crown light the other day. Just to note, I have now seen photos of Gold Crown lights with eight 4' long tubes, like I have, and also lights with four 8' long tubes. Perhaps Brunswick changed the design over the years, perhaps folks swapped out components. I have also seen people post about their T8 tubes...well, mine has T12 tubes. Most T12 tubes were phased out by government decree at some point in 2014, but I think some design improvements to meet the energy efficiency requirements have allowed production to continue. Both T8 and T12 tubes have the same pin spacing at the end of the tombs and will fit into the same size tombstone light holders. T12 tubes were designed to function with a magnetic balance, while T8 tubes use an electronic balance. The power outputs are different; however, each tube will light with either ballast, with the result of having mismatches causing under-powering of the tube or overheating of the tube: both shorten the tube life.
I just ordered my LED tubes and will take photos of the conversion process and post when done in another week or two after the tubes arrive. There is no typical standard set out there for LED and many manufacturers differ in their solutions. There are tubes which will just be a simple replacement in an older fluorescent fixture and will work with one or both types of ballasts. Some tubes can be used with the existing ballasts or with them removed. Other tubes will only work without ballasts. Depending upon whether one wants dimming capability, a particular light temperature, or a high CRI, your options will be with a given subset of tubes or manufacturers.