If you have a 750 Fair Isaacs (FICO), then you'll get top-notch rates. Is the truck at a dealer or private party? If it's private party then like Rex said, try your own bank first and compare rates around town.
http://www.lendingtree.com has worked for a lot of people as well.
If it's a dealer, then they should have access to indirect lending sources that you wouldn't have access to otherwise. Chase Manhattan is a great place to finance.
Keep in mind that the older the vehicle is, the higher the rate will be regardless of your FICO score, but you'll still get better rates versus someone with mediocre credit. What year is the truck?
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