Well the EBay seller for the KZ1000P swingarm offered me a 77 KZ1000 arm instead, so I took that. Is going to go into a 78 KZ650 frame and would give me a little beefier swingarm and just about a 1 1/2 inch longer axle point. However, what I have found out so far on comparing them side by side, is that the KZ1000 arm is about .125 wider at the outsides of the bearing tube than the KZ650 arm and either the frame bushings or the arm will have to be trimmed to fit the arm into the KZ650 frame. Has anyone else done this swap and which side of the problem did you trim?
The other thing I noticed that surprised me, was that the inside of the KZ650 arm is actually wider at the front area than the KZ1000 arm, it looks like it is about 1/4 to 3.8 wider, so it looks like it will actually allow a wider tire on the KZ650 arm.
Just some findings in case anyone is interested in this swap. Have not decided if it is worth trimming the KZ1000 arm to fit yet or not