TOPIC:

Can someone tell me what is the correct seat for 1978? I assume something like that:
 

What is this seat then? I really like it
 

Giuliari at least I think that was the original maker of this type of seat.  There may be others who make them since then.

The original maker was a UK company called two/four and used a dice logo embossed into the side of the the cover. In the early 80's they sold the design to guillari, an Italian company. There was a few months during the changeover where both the guillari signature logo and the two/four embossed logo were both on them together. Once stock was used the two/four logo was dropped and only the signature logo was used. The signature is a bit faint on this one under the kawasaki logo but if you zoom in you can see it.
The two/four logo is clear on the side. 
These are for a z1000 but the black 650 below is a guillari only logo'd seat. 
There are a few companies in the uk that make repop ones. 

I like the Guiliari seats too.
I looked for years trying to buy one.
I ended up buying a reproduction seat cover, and reshaping a stepped seat I had.
I made the rear edge a little high and had to raise the tail a little to close the gap:

 

From this:

 

To this:

 

 

It's amazing what can be achieved with a bit of ingenuity, don't know if you have seen my build Rob, I have just adapted a Triumph Trophy seat for my 82 Ltd