Chained drop down modification AJAX/PHP

I have an existing script attached to a database that works perfectly. It is chained drop downs using PHP, and AJAX to pull data from a mysql database and populate a form. This is for vehicles, it asks for year, then gets a response from the database for the make, then model and trim. The problem I have is I need to be able to run this twice on one page. Can someone modify this script in order to allow me to run it twice on the same page and submit the reults to the next page of the form without messing up the other set? Attached is the code that I am using. to do this query.