The latch system didn't come into use until 2000.
You don't want the seat to move more than an inch forward/back or side to side. Does your car have the shoulder harness or just the lap belt?
If you have the harness, a trick is to run the belt through, buckle it, extend it all the way so it locks and retracts. Then basically sit/kneel on the seat with all your weight and pull down as hard as you can on the belt at the point where it runs vertically into side of door area. Once you release it and remove your weight from the seat, you'll be good to go. Good luck.
If you cant get it to work, go to a local police or firestation for help. Its gotta be right.