Too late, you can get LED kits to replace them...
Use your favourite butyl caulk on them when you install, and that'll be that.
Put some anti-seize on the screws, so they will come apart for bulb changes in the years ahead... Every time a busnut has to fight with seized fasteners....remember to use some anti-seize so it doesn't rust solid again!!!!
happy coaching!
buswarrior