Dave, they are certainly different. However, your forum name (DaveLTD)suggest that you may be comparing the Z900 Ltd to a Z1000 Ltd. these may be the same.
The normal z900 sprocket carrier is the same as Z1,Z1A & Z1B, whereas, the Z1000 carries a rear disk and is different. Some of the differences are.
Shorter length of sprocket bolts
Different size boss for sprocket *
Different PCd for bolts *.
Different shock drive rubbers.
This info * is from memory and could be incorrect, however it is certain that the carriers are not interchangable.
RegardZ