fox body seats and pre 99 seats will. You use the tracks from your car and attach the seats to it. I am using '01 seats, slight mod to the seat pans and made tracks to use with the seats. It took about 2 1/2 hours to completely change them over. I love them. You do need to figure out the height of the seats and gauge them from there. The overall cost should be the factor. I chose a set of leather seats so for 300 plus my time, I'm way ahead.
Asa far as the seatbelts are concerned, you need to check on line for a supplier. There are roughly 3 companies that truly make them. The top of the roof line has an exposed hole which you use for the anchor but you need to fabricate some nut plates which will accommodate the size of the bolt.
Here is a good link to some that I helped the person who wrote up the topic:
3-point seat belt install pictures - Vintage Mustang Forums