Exhaust/int. manifold bolt holes and muffler advice

[hevymetl]

So I bought a new front pipe to replace old rusted one and while removing discovered the old exh manifold was cracked in several places and severely rusted. Ordered new one, installed, but discovered a couple of “soft” bolt holes thAt hold it on. What’s the best way to address this? Also, any advice on a good sounding muffler for this 250 6cyl, that’s readily available? P.O. had a canister looking one with a Toyota stamp on it. The ends are horribly disfigured from a crappy welding job and I’d just assume replace it.

Thanks, John.