Sadly no alternatives out there… Like this plugin most developers hard code the specific fields. We have looked at WP Car Manager specifically, who are keen to develop their plugin further and were the only developer to get back to us promptly.
WP Car Manager also have template files that you can override in your child theme.
Another plugin which got really close was Motors – Classified Listing by StylemixThemes, such a shame they don’t make them more customizeable.
We will most likely modify the WP Car Manager plugin but not sure how yet.
Good Luck.
