so the nut should slide over the bolt then weld it?

 

Use whatever you have laying around that you can make work. You'll be welding thru the center of the nut, onto the broken bolt.

 

I had to do this. Real simple to weld the nut on there. Chevy has a revised bolts available. I ended up replacing all of mine with the newer bigger bolts.

 

I used the SS header studs on re-install. very clean.

ARP Header Stud Kit, LS1, LS6, 5.7L & 6.0L | WS6store.com

 

My old 99 5.3L was the same way as yours. I just let it leak since I was building a 6L. If you are keeping the 5.3 for a while u can weld a nut on there and remove it. And get the bigger headed bolts as iregret mentioned, or a quick trip to fastenal will work too. Hell even my 07 lq4 had one of the bolts broke...

 

I was lucky enough to have 1 or 2 broken off with threads sticking out and 2 more that just fell out. my manifold was pretty warped though and i resurfaced it as best as I could with hand files and it's been leak free ever since.

 

I had zero threads...hope you are luckier than I was

 

the bolt is actually flush with the outside of the manifolds so im hoping when i pull the maifolds off i can just get them out with pliers or something and some good old pb blaster! also going to get some replacement bolts, you guys want a write up when i get these headers in with pictures?

 

PB Blaster is a good choice

It sounds like you may have it easy, but I would fix them ASAP so vibrations don't crack them off flush with the block.

 

Unhook your battery and computer before you weld, its not common but I seen a PCM fired from not being unhooked and vehicle welded on last week. For a broken manifold bolt mind you.