Thank you very much for interesting reading Mike.
The 2xCB750 has good looking left side with the typical alternator covers still there.
Front engine has a belt to rear engine crank, stock gearbox still there with stock front sprocket -drive chain- wheel?
"Std" clutch handle both engines?
If like that, lots of torque to handle for rear primary chains, prim hub, clutch and gearbox.