Heads-valve covers, differences.

What is the difference between the round end and square end valve/cam cover heads?

Would this help?
www.aperaceparts.com/tech/techkz1000.html

The earlier Z1's,KZ900's and Kz1000's had cam plugs that would come out if not secured.

The later Kz1000's and Kz1100/GPz1100's had a bolt going through the valve cover/cam cover holding the cam plugs in place(4 places).

excellent link, I have been roving that site, but it is a biit hard to find some things.