I mounted a pair of allmost brand new takeoffs from a Harley Road King on my GL1100 that I got at a swap meet for $20.
The first thing a lot of Harley riders do is replace the stock exhaust with aftermarket and there are quite a few avaliable cheap.
I sawed off the old rusted out mufflers and the new mufflers fit right on the pipe.
I cut the mount off the original mufflers and welded them on to the new mufflers.
Not as quiet as original Goldwing mufflers but produce a pleasing rumble.
Peter