the D16Z6 is an OBD1 engine and your '92 is an OBD1 car. The Z6 in it's original form mounts right into your '92 with almost no changes at all. And yes the Z6's ECU is the P28. Make sure you have that.
But you can run the engine OBD0 if you really want to. But it would need an adapter harness at the ECU. You'd be hurting yourself if you did that though.

It really depends on how the original owner converted the engine to work in his 4th gen and if he did the swap to run off OBD1 or not.

Going to basics... what have you checked? does the engine have spark? is it getting fuel? does the starter simply spin and spin and the engine never tries to run or does it sputter? does the starter not even spin?

I'm curious... why do you have a MSD setup? Honestly, unles you're going boost or really high compression it is overkill and a general waste of money. Plus if there is something wrong with it, it certainly would make the car not start... (unless you mean MSD wires only, that's different)