This set of hardware is used to hold the seat frame to the rails and the seat rails to the floor mounts.

Low head, steel, yellow zinc dichromate plated bolts with a hardness rating of 10.9. 

928 (78-84)
944 (82-84)
911 (75-84)
930 (75-84)

or if your require parts are listed below.

They are replacement for Porsche part numbers N 0147612, 90011912901 and N 0120064