There are so many places that you can hook up ropes with hooks.
Take a piece of cardboard and place it on the ground so that you can take a good look under the van.
All vehicule have places were towing ropes can be attatched, in case of emergency.
I am sure that you will find a place to hook up your ropes.
Use S hooks, that is what I use on our van.
Happy float fishing.
chris