Without being able to directly connect to each database ( username and password) and have database tables and fields, you are left with searching tha web pages manually.
For autotrader do a search and place that in your form with the data from your site
from there you can place your data in the above text line and use perl possible asp to get the web page. Once you write that file to a text file on your server or site, you can have perl or asp scan the code... Have it delete everything before the
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tag and there should be another tag ending it. the items left would be the card ads and pictures you want.