Start here:
http://www.flhsmv.gov/dmv/faqtitle.html
If the current owner had a title in his/her name, they can get a new title easily.
If the seller isn't the legal owner (title holder), you may be able to request title holder info using the 90510 form on the forms page. Careful, you may end up buying the truck, then have to buy the title from the legal owner.
Forms:
http://www.flhsmv.gov/html/forms.html