Steve,
Here is what I did, when I got my Van about 2 years ago, with a faulty
exhaust system.
I replaced all the pipes and gaskets, and then found out what the
muffler was going to cost , and I almost puked!
I measured the diameter of the stock muffler, and went to Pep Boys, and
purchase a turbo muffler of the same diameter.
I cut off the mounting flange, off the old muffler, welded it to the
inlet side, and hung the turbo, with the stock hanger and all.
It is a little shorter, so I added a chrome extension, cut at a 45
degree angle at the end.
Looks good, growls like a Porsche, and it seems to have helped out a
little in performance, having no, or little back pressure.
Cost?
$15.95, plus 1 hours labor.

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Terry 85 GL