If I am understanding you correctly, the factory stud's for /6 engine's were 5/16" on both side's of the stud's, only being on the head side the thread's were 5/16 x18 coarse thread, and the other end of the stud is fine thread 5/16 x 24. I know someone may have some used one's here on this site, but also do a search for these stud's here, as I have read some info on where guy's are saying who carry's them stud's too. Good Luck!
