The stock Fiero "bulkhead" connector isn't a connector at all. All it does is provide a sealed "pass-thru" the bulkhead/firewall. There are actually no wiring harness connections inside. It is factory assembled over the stock wiring harness with heat activated sealant/glue. This means you can take it apart if you heat it up (with a heat gun) and remove it from the factory Fiero wiring harness and then separate the glue from it so you can reuse it on another harness.
After removing it from the Fiero harness, you can install it on the harness you custom make for your 3800. I do this in all the swaps build. I custom modify the stock 3800 wiring harness to run thru the firewall in the stock location so I can mount the 3800 PCM in the stock Fiero ECM location. After you are done with all your wiring work, you can seal up the "bulkhead connector" with the RTV of your choice (I use Permatex Ultra Black in the full size caulk tube so I can squeeze enough into the bulkhead connector to seal it properly).
OVERKILL IS UNDERRATED
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