LT! to LSX conversion: Wiring harness question
 

I'm not sure this is where this goes, so my apologies to the mods if it isn't in the correct spot.

I've just started the teardown process on my 96 SS. I'm planning on swapping in an aluminum blocked 454+ ci LSX (probably RHS). I've unhooked the wiring harness from the engine/transmission/computer, but there is a small bundle that goes through the firewall on the passenger side, just behind where the computer mounts. I've started to cut apart the wire cover and try to see where those wires come from, but I'm not sure... Do I need to go under the dash and remove the bundle going through the firewall or do I need to split out those wires from the rest under the hood?
Anyone have any help as to how to proceed? Thanks.

Here is the progress so far:
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Attachment 20711

It should be just a grommet I believe. I don't remember exactly what it was but I just did it last weekend lol.

So I do have to actually remove the wiring going into the firewall? I thought all I had to do was split out what wasn't the engine harness. I am sending the harness to Speartech for the the conversion. (I guess.)