Well, I set about fitting up the new parts I got today. Mixed results, unfortunately.
The rear wheel was a happy surprise, the drive spline matched the rear end, the drum brake fit perfectly, and the CX650 spacers fit as well:
I'd done well, until I looked at it from the back and noticed this:
The offset is all wrong.
This wheel came off of a mid 80s VF750, which has the final drive on the left-hand side instead of the right like the CX. I had hoped it wouldn't really matter, but no such luck, obviously. Crap. Now I have to figure out something else for the rear wheel since I definitely can't use this one and I'm not going to use the 15" stocker since there are no tires at all available for that goofy cruiser size.
But, on the bright side, the XL600 forks fit nicely, I was even able to use the CX axle so I know everything is in the correct alignment.
The CX front brake bracket won't fit the XL forks, but making a new bracket won't be too terribly difficult. (The mess in the background is my other project, currently on hold while this one is in progress - a basketcase GL1500. What a headache, all that plastic)
I hope I can figure something out for the rear wheel. There is, if all else fails, one option - I'm told I can pull the rear cover off the engine, then swap a CX500 output shaft so that I can use the CX500 final drive. This would be a PITA since the final drives aren't a bolt-on swap. I'd have to cut off the flanges of my 650 swingarm and a 500 swingarm and then weld the 500 flange to my 650 swingarm.
My best bet now is to fit a Comstar from a CX650 Turbo, but those came with rear disc brakes, so I'd have to swap all that nonsense over and then fab mounts for the caliper bracket. The plus side would be gaining a rear disc instead of having a drum in the back, I guess, but doing that will drive the cost of this project much higher than I want.
I'm open to ideas, if anyone knows of a Honda shaft drive bike that has a drum brake and a right-hand shaft drive, let me know. The problem is that the CX650 uses a different drive flange than most other Honda shafties of the era.