even if it is legal i wouldnt do the car seat thing.... pretty sure being bolted to the floor in a car seat would equate to an awful ride, at least on the seats there minimal padding to absorb some of the bumps.

but i do recall seeing someone who replaced the pin in the hinges with a bolt and wingnut setup that made it relatively easy to just pull the seat out but leave the brackets in place

i was also considering bulding a subwoofer box along one of the sides of the cargo area that could double as a seat.. it would be easier to remove than the seats... accessable through the tail gate.. and supply me with some nice bass.... hmmmmmmmmmmmmm