help!? bassani o/r x install

Use a 1/2" ratchet and spray plenty of penetrating lube on the studs. If that doesn't work then get an impact, air or electric. Most places rent electric ones. You can try using a breaker bar on them as well. They are 1/2" studs so you will really have to pull to break them, unlike the generic 3/8" ones GM uses on the Z28. I snapped one of those when I installed my friend's pipe on his 98Z.

If you break them you will have to remove the header and drill out the old stud, since they are welded in place. I see you have Bassani shorties listed as an upcoming mod. Now may be a good time to just go ahead and install those as well. That way if you break the stock header stud(s) you will not have to worry about it.

The studs on my stock headers werent welded in place. The nut on the header of mine was on so tight that I actually pulled the stud out of the header as a whole.

I suggest letting some penetrating oil sit on the studs overnight if possible or at least a couple of hours. I'm not talking about WD40. I'd get some real good, thick penetrating oil. WD40 is too thin.

Then go out there after its sat for a while and find yourself the biggest, longest socket wrench you can find. Get underneath and put your heart and soul into getting that nut off. Sometimes you have to yank on it harder than you think you should. My first car they were a pain in the butt, but my last car they came right off.

Good luck
Chris