Back in the day a few people did the 916 arm into a hoop frame conversion. You'll have to weld in a new suspension link pivot point and machine the cases back.
AK did a superb one, not sure he or CK (his wife post on here much now), grunter did one. Might be worth messaging grunter to see if Viv is still in business. He used to machine crankcases for the conversion.
M900DOM did one of the best originals, however I haven't seen him post in years.
Been looking for the early pictures but they don't seem to open anymore
