Hello,
I got a kit from Roverland parts for $1250 plus shipping. Not too difficult to install, except the rear seat-belts. Also be careful not to let the retract if possible. They have a gravity/position based mechanism that you will have to play with positioning the unit just-so in order to get the seatbelt to pull out again. I had to find a diagram online as to how they are fitted behind the plastic rear storage area. I did not have any instructions with the kit. You end up with some duplicate parts from the 5 seat setup. Check it out here:
http://www.roverlandparts.com/LR3-jumpseats.aspx
All the mounting holes/sockets are on the vehicle already. There is additional hardware to install into the floor to attach lower seatbelt holder/brackets etc. There is also different clips/bracket the seats pop into. I can't remember it all now, except it would be easiest to have another 3rd seat vehicle to compare too, or have ready access to the donor vehicle to make sure you get everything. There is different large carpet piece with holes/slits for different mounting points. It probably 50+ lbs. with the padding, different long bracket piece that goes on either side of the carpet (next to the wheel- wells), different or replacement foot or support that the seats clip into when hidden in the floor, different rear beam plastic cover that houses the seat-belts and has a slot for them to come out of, brackets for seat-belts, seat-belts themselves. BTW, you have to bolt the seat-belts into the frame/sheet-metal behind the storage area which is a PITA and will likely need to remove the top of the rear storage to do so. Not terribly difficult, just a pain (like removing the existing carpet from the under the storage area on either side and working the new carpet into that same area). Going from memory here, but there is a lot of additional and alternate hardware outside of the seats themselves.
