There's been a few posts on exhaust replacement lately so I thought I'd share a find.

IF you decide to do it yourself, there is a very nice tool to help you put new pipes in old mufflers. You know how the old clamps deform the pipes well this tool, LISLE #32500 is the perfect tool. You place the tool in the deformed pipe and as you tighten the bolt, these fingers expand and and round out the pipe again. I've done exhaust repair for years (and hated it)I stumbled across this and bought it. It's the best! Another secret of mine is using Liquid laundry detergent as a lubricant to help join the pipes. Slippery stuff.
Other companies make them but they work with a hammer. I didn't like the fact that you adjust the tool for the pipe diameter then you have to bang the tool through the deformed pipe. It's very spastic when the pipe is on the car and it beats the heck out of the welds if you are trying to true up a muffler.

http://www.lislecorp.com/tool_search_results.cfm?PageNum_rsList=1&Search=exhaust
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'75 Jeep CJ5 345Hp ChevyPwr and two motorcycles: it wasn't Volvos safety , it was Longevity that sold me