I have a 1974 chevy C10 1/2 ton (ok redundant I know), chevy stepside. 350 with what I was told is a 450 transmission. Not sure on that...but..the truck developed an exhaust leak on the way home (within a few miles of home). Seems to run rough as well and it may well be that when replace the flange gasket or doughnut gasket, (manifold to exhaust pipe), the whole problem clears up. The leak seems to have the whole truck shaking. Anyway, I will pull the exhaust pipe tomorrow. I Soaked the bolts with penetrating oil today to try and loosen them a bit before I pull them. I hate exhaust problems. If this doesn't go easy I will head to the muffler shop!! Anybody seen an exhaust leak cause a rough idle??