Glenn,
You asked for our thoughts - I may be wide of the mark, but here goes!
Firstly, you say the cam and gear have to be separate to insert them into the crankcase - I don't think this is the case. As this engine has automatic inlet valves and is a flat twin, then the camshaft will have just a single lobe that operates both exhaust valves. If this is the case, then the cam and gear can be rotated to a position where it will go into place and then turned to the correct timing position, and then the crankshaft inserted into the crankcase to mesh with the cam to give the correct timing.
You also mention a distributor. Bearing in mind the age of this engine, it probably had trembler coil ignition - in which case a cam or flat on the end of the camshaft probably operated a make and break for the trembler coil.
Regards,
Eddie.