Yes I have one in my 512 also noticed that studs were not arp called seller and was told they were made by arp for his application I dont believe that. But he assured me that he has many in use at 900 hp levals with no problems I did use them and as of yet had no problem at about 650 hp but is always in the back of my mind and would like to replaceat some time for peace of mind.Also the the extra studs reccomended for rear main will not work so dont bother with them I guess the studs are prbly better then 40 year old bolts and the quality and fit of girdle makes it a decent bargin.