Hi Rushman
I do know that the header pipe is a different bend angle to the 90 Deluxe/Trail/Mountain. The 90 Sport is different to both 50 and 90s. As for the muffler, the baffle is different on the 50 and 90. It may fit but the performance using a 50 muffler on the 90 may be affected. The mufflers may be different in their homologation.
Others may know more.
Cheers
RayK
Australia