frame number seat latch question

hello can anyone help me with a frame number answer--the frame number is z1f-087319 but it has a later style seat latch bracket welded to the frame--it has a cast aluminum engine in it i have to go to my other building to get the engine case numbers if you need those also--any help would be appreciated!! thanks!! what year is this?

You have a 1976 KZ900-A4. The seat latch as you describe is correct for your bike. Earlier bikes (the Z1 series) had the drop down post latch. You might also join www.z1oc.com as that is a group focused on Z1/KZ900/KZ1000 bikes...lots and lots of knowledgeable folks.