Seat Belts! I found some 3 point belts on Ebay for $80 and here's how I installed them. The first thing I did was drill a hole in the flat area between the quarter window and the door jamb. I went about halfway up (I sat in my Blazer and used that mount height from where I sit) and drilled my hole.
Next I took the flat mounting plate they give you and drilled a hole in the end.
The hole is to hook a piece of wire to and then lower it down from inside the top area (it fits perfect) until you see it in your drilled hole. It's a little work, but once you get the bolt about halfway in you can pull the wire out and tighten it up
Now I used the back plate/rail area behind the seat to mount the retractable part of the seatbelt. Next I made a couple of mounts from 1 1/2" x .125" angle, drilled some holes
and mounted these to the floor. I used another set of plates that I had (like I used in the door jamb) and used it under the floor to hold the bracket in place
After I finish the carpet and seat, I'll paint the brackets and then it'll look finished.