Google shear strength of grade 5 vs grade 8. Grade 8 has greater tensile strength but weaker shear strength.really ????? grade 5 bolts for installing a clutch and pressure plate -- somebody may have went to class for nut and bolt tech but they were not listening --- factory used grade 8 --- if you want to use grade 5 bolts in this application -- the next time you take your car out for a ride get a grenade ,pull the pin out and jam the arm under the console or seat -- believe me you are not going to hear any clunking before it lets go.
look up clutch explosions on you tube.