What you really are trying to do is split the cases without taking the top end apart. I don't know if that is even possible.
Just thinking out loud for a minute...
You would need to pull the engine from the frame, pull the valve cover, remove the cam chain tensioner, then pull the cams - to get enough slack to get the chain around the crank, The flip it over and split the cases. Then remove the counter balancer chain, then pull the primary shaft and primary chain. Finally remove the rod caps and push the poisons down a bit. Then you could swap the crank
Maybe in theory it could be done, but you may just be the first person in history to try it on a 750 twin. Kawasaki would have you completely disassemble the entire engine to get to the crank. So trying to shortcut the whole thing and swap a crank may not be possible.
If I knew what I was doing all the time life wouldn't be any fun.
'80 KZ650 E 700cc, dyna ignition and coils, frame up restoration, daily driver
'81 KZ1300 A3 full restoration, custom big bore pistons, 1400cc 6 cylinder super bike
"77 KZ650 B1 - Barn Find, work in progeress
"74 Yamaha DT 400 Enduro