360 Magnum teardown

I have one in my 01 Ram that's got 185,000 miles and if it has cracks it sure doesn't affect anything.
I also just put a 360, 115,000 in my B body Charger, I didn't check for cracks and it runs fine too.
I used the Chargers original 318 exhaust manifolds, so I think your 340 ones should work fine. You just need to address the heat exchange valve flapper thingy (if yours have one).
Good luck