Thanks for all the responses. Here's an update on things that have occured since I started this thread:
I interviewed at a small cargo carrier that flies Cherokee 6s, 402s and Aerostars. The guy who helped me get the interview told me that the boss and all the pilots wear business casual, sometimes even jeans with a collared shirt.
So I wore a pair of khaki pressed slacks, a dress shirt, and no tie. Got the job and started training yesterday.