[Landseer]

You should cycle through the grounds and clean them.

In particular, get the two that are on bolts above the CE panel (passenger floorboard), firewall. You may need to remove the wooden covers from that area.

Also, get the one that is in the trunk area, drivers side slightly, that the negative battery cable is attached to.

Also, take apart the 14 pin connector in the engine compartment against passenger fender and clean out corrosion.

The charge exciter wire in particular, along with other harness wires, fail. Sometimes they break inside the insulation or fail intermittently. Its the little wire on your alternator. You can check continuity by putting a meter between its end and terminal #1 inside the 14 pin connector. It is also the same as terminal 8 on the back of CE panel plug O.

That said, the alterators seem to fail often. My strong recomendation, at least to get started, is go to the auto parts store and get a 105A alternator listed for the 1988 V6 Camaro and an off the shelf pigtail for it. Connect your alternator wires to the + terminal bolt. Except the little wire, the exciter wire, it should be attached only to terminal L on the pigtail Connect none of the other three pigtail wires, they need to be removed. This should get you going.
I wouldn't trade-in the core, it might still be good, you could have it checked, it can also be rebuilt as parts are available to the DIY'r. The vent cover will not fit, you would need to run without or fab one. Note that the fenderwell on the drivers side has the vent hose, which contains an important outside air sensor used by the Bosch fuel injection system as data, so don't axe it.

The conversion is economical. Again, your alternator might be fine, then what I've suggested for the conversion is not so sensible, you can figure out the order in which you test / try stuff, but this information should help you.