Hello got 82 750 ltd

So much has been done to this bike before I even got it. You may refer to my "profile" image for what the bike looked like before.
The seat is off a Gpz900
The head is off a Gpz750 - meaning the tach doesn't work. Something about the GPZ tach being digital and the KZ tach mechanical. I bought an '80 gpz750 tach but I lose the fuel indicator light - not sure If I want to do that til I'm more familiar with the mileage etc.
One of the covers has shift linkage attached to it, just hanging in the breeze, on the right hand side...but my shift stuff is securely attached beneath the engine.

I'm not sure what other modifications were made. I added the rear pegs and new mirrors. Other than cleaning out the carbs and float bowls, everything else has been cosmetic.

I still need to replace the fork seals (I have new ones still in the package) and replace the head gasket which is leaking. Do I get the gasket for the GPZ750 or the KZ750 or is it the same? Seems confusing.