I know of a C2 chassis located in Warrensburg Missouri. It has the correct swing arm, I know because I bought the Boge LTG shocks off of it.
The air box is like most these days, back side is broken out. There is a place in Arizona I believe, AMS Racing, that has a fiberglass replica of the airbox, but it requires the hardware off the original.
I know parts in the "Lower 48" creates shipping and currency exchange problems, but in the end it may be the only way to get what you need.
Kenny