There is still several custom shops making the frames. Led Sled, Bitter End, L and L choppers as well as Voodoo Vintage who makes a frame less head stock so you can weld the Buell head on and retain the VIN. No messing around with Da Man there.
I don't know of a softail version but there are softail frames for sportster motors that I'm sure could be made to except the Buell plant i ones back or backside would require some spring in the back.
Personally a rigid would be first choice. Just a much cleaner look and more true to the breed.
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You meet some of the best folks behind bars.