ARP sells both the heavy and normal duty nuts. I think the heavy nuts are around $8.00 each. Either type will work. Any major nut and bolt manufactureing shop will be able to supply them. Sorry about all your troubles. I too have had stud problems. My set of the Kens H13 material 270,000 psi studs broke two of them. Found one laying in the driveway one day. Thought it was a 3/8 inch extension I forgot to pick up. Nope... So I bought a set of what Typ4 used. They are the ARP 7 ibch long 200,000 psi studs. While torqueing them down and loosening them up the 5 times required I gaulded 6 of them. This was using there ARP molloy lube. So off the next day 120 miles to the Factory and they gave me 6 new studs with nuts. I had a great talk with there long time engineers about these studs. They really know their stuff. Most important thing they said was the threads need to be rolled and not cut. Joejohn... I know you are cutting your threads and I really want to know how they hold up to the stress tests. ARP can make a set with a 330,000 psi breaking strength but.... You can't touch them with your bare hands... The moisture or sweat off the hands starts a corrosive action and they braks at the point. Also if you drop one it breaks like a glass bottle. Really some exotic material too. About $1800.00 per set too....