As a general rule, I like a color scheme to work with the lines of the car; someone already mentioned vintage PS schemes, which often worked with the side contours.
As for the blotchiness, that sounds like a pressure or application problem, though I've never sprayed that particular paint. There are a lot of modern car colors to choose from, but formulation & coverage is sometimes an issue. It may be that you need to work with another painter. If you can get your hands on the "what's new" issues of National Dragster, there are a lot of ideas you can find there, too.