Most of the retailers like OG Racing will include the spring loaded fastners that clip into your eye bolts or anchors. In fact if you buy the whole setup from them, they will include all the hardware.
www.ogracing.com Also, Brey Krause make some sweet anchors that will allow you to keep your stock seat belts. Just make sure the harness loops over a harness bar or the like, the belts must be close to 90 degrees to your shoulders. While your at it, go with the six point sub-belt which will mount under your front seat rails. You won't have to poke a hole in your floor and this will work with a stock seat.