It's a great looking car as-is, but I can understand, a car is never done.
I think if you're going to paint it, I suggest getting rid of the rear trunk/quarter chrome, fill in the side markers (at least make 'em flush), and maybe a front rubber bumper.
Cheap mods would be to take out the rear backup lens and get all four taillights to light up. Round rear lights are the best out of all the 'Cudas IMHO.