it's all ls's they pop manifold bolts.. even my ls3 car did it.
definitely don't need to pull the head.. just use the clamps or pull the manifold, they usually aren't tight in the head. maybe in the rush belt as everything is haha. but normally if any is showing you cam unscrew them pretty easily. if not, I just build up a little bit of weld with a cheap mig and screw them out. since the head is aluminum it doesn't try to stick to anything but the bolt. few tacks, clip on vice grips and it should screw out.
personally I hate header/manifold bolts.. even good ones are meh. I perfer studs with flanged crimp lock nuts. never have to touch them again.
I used the Dorman kit for mustangs on my car, took 2 kits but they are super cheap, good 10.8 grade but I believe they now sell a ls kit too.
I'm all for arp but I feel like header bolts suck enough I didn't want them haha.
they don't make them anymore, but old sbc days they had some header bolts that were drilled and tapped in the middle for a set screw. once you tightened the header bolt you tightened the set screw and it flared out the bolt and locked it. those were nice but expensive.
