289-302, 5.0L with 351 Windsor head, 7/16"-14 cylinder block thread.
M-6049-J302, SVO high port & M-6049-L302, AFR 185 with 1/2" holes Edelbrock aluminum , GT-40 style with insert "T" washer.
For openers, ARP uses a premium grade 8740 alloy that is rated far superior to "aircraft" quality.
Each stud is placed vertically in special racks and precisely heat-treated to 200,000 psi.
This procedure ensures complete heat penetration and great results.

More information in ARP´s catalog here.