Don't scrap the damaged manifold- - - -with a little cleanup and some careful pre- and post-heating a good welder can repair it. There's even nickel-alloy wire available for a MIG welder for such repairs. That's the area of the manifold that carries the exhaust gas from the heat riser, so there shouldn't be a vacuum leak from it, just exhaust.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!