where to buy exhaust?

I have a Summit 2.5" system on my Duster with Doug's headers on my 340. It fits great, no issues at all with the pipes being "thin". I did the whole install myself, I did have to trim a few of the pipes, mostly the final length of the tail pipes but I also took a little out of the mid pipes. Nothing crazy, and what I would expect from a somewhat generic kit. It was easy though, all I had to do was cut a few inches straight off the ends to put the mufflers where I wanted them. It has held up just fine over the last 4 1/2 years that it's been on the car, the whole thing still looks new. The only issue that I had with the entire system was the mufflers, the original mufflers included with the kit had crimped edges that started to leak exhaust after maybe 6 months or so. I switched to welded DynoMax Ultra-Flows, love 'em. I drive the car all the time, and commute on the freeway. There's a little drone at some rpm's, but it's not bad at all. My cruising RPM to hold 70mph on the freeway is like 3,300 rpm, no issues at all there. Oh, and the little plastic clip thingies they had to hang the tail pipes didn't last all that long, but I expected that as soon as I saw them.

I just bought a second Summit kit for my Dart, they have welded mufflers now included with the kit that I'll probably run. I love the Ultra-flows but they are kinda loud, my Dart is going to be the "easy" car- power steering, automatic, and probably a little quieter. If I can resist the temptation to buy another set of ultra-flows :D.

I don't know if Jeg's is supplied by the same manufacturer, but eventually all of my cars will have the Summit kits. Great bang for the buck.

As far as there being tight clearance on the tank, that's how EVERY system is. There's very little room to sneak the tail pipes by the tank and springs, the larger you make the pipes the harder it gets. But I was still able to get my Summit kit to clear fine, even with a 1/2" inboard spring offset.