I love Customs, alot of them have perfect paint and a great stance, but some of them just don't have that perfect fit and finish, one might expect. Door gaps are off, the deck lid doesnt quite fit right, etc. etc. In order, to take a car to the next level, I feel it's important to address all these issues, way before the body filler comes out. Here are some scans from a 1950 Ford shop manual, that shows some simple and clever techniques, some people might not know about. The illustrations show the 1950 Ford passenger car, the might Shoebox, but it will translate to other cars as well.