[Rubone]

I suspect it mostly had to do with budget issues. Buy a couple beater bikes, who cares what model, and build your dragster. Physical differences and aesthetics would have nothing to do with it, just cost. When Knuckles and Pans sold for $100 bucks anything was possible!
Robbie

 

[Rubone]

I just want to know how Jerry kept the knuckle from passing the pan.

It just pushed it along with a piece of stiff chain!
Robbie