It could be an aftermarket wheel, I've seen that spoke pattern before but I can't remember where. Those discs are def not cb750 discs anltught they look thick enough that they might work, oddly enough the speedo drive looks to be a 1970-78 750K speedo drive.
could be a nighthawk wheel.
It would be worth the $25 bucks for me just to see what it is and if it fits. Heck I would even pay shipping......