rbok wrote:
What I would would be interested in are brackets and exhaust manifolds that you could use with stock Harley Davidson mufflers.
I would hope that replacement mufflers are an infrequent purchase, making the cheapness of HD mufflers a non-issue...

And I've not been particularly impressed with the "quietness" of any factory Harley Davidson bike, since they push the limits of what the EPA will allow, to preserve that "patented Harley Davidson sound".
There are some vendors selling tube-type muffler systems (header pipes on out), so getting a "generic" system isn't the issue.
Top Shelf Parts will sell you complete MAC systems for $330 to $350 + shipping, for example. But that changes the look and sound of the bike, for better or worse. It's certainly an inexpensive (relatively) way to go.
I must admit, the stock GL1000 muffler is a PITA to remove and replace, but it is
quiet. And that's why we're looking at some way to fix or duplicate the system.