It looks like you're new here. If you want to get involved, click one of these buttons!
1959-1975 Pontiac Bonneville/Catalina/Grandville
Also this search engine:
and also this site has good listings:
Good luck in your search. I think you're wise to limit yourself to convertibles and coupes. I'd try and find a car with the most options and in the nicest colors, too....and the bigger the engine, the more valuable the car will become. As you probably know, originality counts for a lot as well. Any car that has been painted the wrong color or modified in some way is worth far less than book value.
Also, I don't know if it matters to you, but 1973 and older cars are more valuable in California because they are smog-emempt.