Looking for must haves to build a car that is a personalized expression of oneself seems to defeat the point of that personalization. The one thing that all the great and copied customs of any era had is symmetry and flow. Make it smooth, pleasing to the eye. There are plenty of ugly cars, built for show points, and ideas that did not mesh. Simplicity, flow, easy on the eyes. Beyond that, it's finding the parts that fit the body. Accentuate what the designers built. Be like Sam .
Or a Cabriolet??? I'm sorry, but I'm just not a Tail Dragger kinda guy. I still prefer mine with a little bit of a California rake.