What you want is the Hatori SB-23FH.
But, they are unobtainable.
I would not use the 91 / 96 pipe on the 120.
The Hatori are tuned pipes and they are designed to resonate and scavenge exhaust gases from the combustion chamber. This helps pull more air / fuel mix in with each stroke.
Using the wrong pipe on the 120, even after trying to match the header to the flange, may result in overheating and a drop in performance.
The Funtech pipe is a muffler. It does not boost power.
I think that may be the worst choice to modify to fit.
I have been told a company named "M Studios" has taken over the Hatori line of pipes and manufacturing.
But, that one does not have the isolated header / pipe design as the Hatori pipe did.
A-Main has it listed, but Out Of Stock:
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