[Tony D]

Hydraulics...

Sounds like hydraulics, but did you keep the same clutch throwout collar that was in the fivespeed, and keep the same pressurelate? L28 to L28 shouldn't pose that problem, but you never know. Why did you pull the engine at all? this is not required to do a tranny swap. This begs the question, did you swap the entire engine/tranny from the ZX into your Z? If you did, what electrics did you use, and what alternator did you use?
Need a bit more specific information to really help other than grasping at straws---will check back later sto see what's up...

 

[Tony D]

Nothing more specific...

So I checked back, nothing more specific, so here goes:
Everything on the late model EFI system will pluginto and function with an early EFI ECU. I did it in my 76 for a year until I got my early non-EGR manifold ready. I ran an 82EFI intake and manifold with all the sensors hooked to the 76 ECU. Make sure you ahve all the connectors hooked to the correct place, and that they aren't all corroded. Make sure you have a good ground. You CAN use the late model internally-regulated alternator on the early car, and it will charge and run fine, but your red light will be on in the voltmeter, and you will fry the external regulator.
As for the clutch not releasing, or grinding going into gear, your pressure plate is not releasing. Again, are the components ALL from the same transmission? I.E. did you take the clutch, pressure plate, TO bearing an collar ALL from the same transmission setup? 9 times out of 10, when a problem is arising like this, and the pedal functions, the wrong collar is installed with the wrong pressure plate.
Keep at it.