For the Z1, Z1A and Z1B the round tail-light bracket is different from the one for the short guard. Also, although I have seen the Z900 square tail-light bracket fitted to the long and the short guard utilising the same bracket, I believe they are slightly different.
Note that the Z900 long guard will fit on the Z1B.
The test is that two fingers should be the distance the lens protrudes from tail and one finger should just fit between the tail and the lens.
This is how a standard a long-guard Z1000 looked.... I believe it is incorrect (Wrong bracket)
This is how it should look IMHO! Using the two finger guide.
The difference are also on the Z1etc long guard.
BTW the brackets are coded with a number stamped on the bracket. Don't ask me the numbers!
RegardZ