Broken Head Stud
 

Has anyone ever used this tool? Stomski Racing Exhaust Head Stud Repair Kit. or recommend replacing only the broken stud(s) and not all of them?

I have used several tools of Stomski s and they all have worked as described. The oil cooler pressure tester, the circlip installer, and the shifter swivel to the trans.
If there is threads that are useable, why would you replace the studs, there is enough real work that needs to be done. I do believe in a set of burning tanks and torches.
Bruce

get the one from a quiet boom, here on pelican and save some $$$$.

Since you asked...
I broke a few exhaust head studs and I replaced all of them with ARP studs, for my thick flanges the P/N's are:
(1) 400-8005, 4-piece kit and (1) 400-8015, 8-piece kit. This will cost you more than the stock M8x1.25x57mm studs, washers, and nuts, but you will sleep well at night knowing that you will never break another exhaust stud, I know I do.

Mark