just an idea

Well, my experience is this.  I took out the rubber floor mat and padding of my 92 Chevy Pickup because of a rusting issue(please no jokes about Chevy rust), and sanded and repaired it all.  Anyway, before I put it all back together, I coated the whole floor with spray on truck bed coating.  Similar to rubberized undercoating.  I coated the rear wall behind the seat up to the rear window, and the floor all the way up to the firewall under the dash as far as I could get. 

This made a pretty good difference.  It took two cans to do a nice heavy coat, and my truck cab is only a regular, non-extended cab(to let you know how far two cans will go).  Also if you do this, you have to be able to let the vehicle set for 24 hours because it will need that long to cure.  The smell will take a while longer to go away.  But it will air out.