If you are looking for the DUI statute as it appeared in 1989, I believe what you would need to do is look up the "Laws of Florida" from prior to 1989. The Laws of Florida are posted on the following website: http://www.leg.state.fl.us/Welcome/index.cfm?CFID=20552656&CFTOKEN=34773122 However, the Laws of Florida from that late back (1989) are not online at that website. Additionally, prior to being filed under s. 316.193, Fla. Stat., the DUI statute was found under s. 316.028, Fla Stat.
Go to your county law library and ask for help. Every county in every state is obligated to maintain a law library not only for lawyers but for those who want to do their own research. Ask the research librarian to help. Old, outdated laws are usually maintained somewhere. In CA I would go to the current DUI statute in an annotated edition of the Vehicle Code and check the history of the law. I believe that would be easier than finding it on line.
If you go to the law library as Mr. Kaman suggests - you will see a set of annotated statutes. Listed with the current law will be a section where you can see the changes to the statute each time that this section was changed. All you have to do is follow the trail of the changes that are listed.
Unfortunately, the online Florida Statutes only go back to 1997. For years before that, you have to go to your local law library. You might try the library at a local law school. For statutes after 1996, you should look here: