Help!! Exhaust manifold leaks

[mhicks]

I got a '73 from my dad and he bought it new. He has apparently replaced the driver's side exhaust manifold with a newer one. It looks like it had 4 tubes coming out of it and I assumed they went to a sensor of some kind. Well, the tubes have been bent over and they worked fine for a while. Now the tubes have rusted out and pitted and they leak. I tried unscrewing the flange nut that goes around it but it broke off. Does anybody know how I can plug those holes so they won't leak. I really don't want to replace the manifold.