Exhaust manifold, not head.
The number of studs doesn't really work. A lot (all?) of the 92 engines have 7 studs for the manifold like the pre revision cars. I've owned 2 92s, plus 3 RC engines, plus I've seen several more. All were 7 bolt manifolds. The only 9 bolt manifolds I've ever seen have been on my 2 93s. You're right about the alternator bracket though, they are different. The one for the 7 bolt only works for the 7 bolt mani. The one for the 9 bolt will work for either. Also I believe the 7 bolt heads have the 2 extra stud holes. Though some of the early heads (90?) might not?
IIRC the quickest way to tell the engine itself is the 92/93 has a throttle opener (it's a vacuum diaphragm) on the side of the throttle body.
Also, the pre revision cars have an oval connector for the alternator harness. The post rev cars have a triangular connector. And the knock sensor connectors are different.
IMO the most important thing is actually the ECU though. The post rev ECUs have better diagnostics. Other than the part number you can tell if you open it up. The newer ones have 2 circuit boards. The older ones only have 1.