6 cyl (292) manifold questions/issues

[May70]

Hello,

I have a 70 c20 with the 292. It had a bad exhaust leak where the two manifolds flange together (along with a valve cover leak). I began taking the manifold apart and found one of the studs looked like it had been broken off previously. That left a nut and a single bolt on the forward side for me to take off and the manifold should have come apart... The only size that somewhat fit the bolt was a 14 metric? The head wasnt rounded off either so I am not sure what happened there... Well the bolt head broke off when I was trying to take it apart. Tried soaking in PB blast, heating etc and it was firm.. I still was able to pull the two apart and see the flange. It looks like its had some history with repair attempts. a couple hair line cracks, some sort of gasket making materiel that resembles jb weld, maybe some actual welding was done. Any way, I did some grinding to get what you see in the pictures and its still not flat.

Does the bolt that broke off (pictured below) go all the way up through to act as the carb mount? The bolt looks STUCK good up in that hole, not even sure if I could get it out. Ive read a lot about these being prone to issues.

Thoughts? is this one worth messing with? What are some alternatives? I see ebay and even rock auto has some re manufactured exhaust manifolds but they have bad reviews for fit etc.. If I bought headers I would have to buy a new intake manifold etc. Not sure if that is an easy swap with orig carb.