Electrical Another plea for wiring help

I am down to the last bit of wiring as I trace all the looms throughout the car. I am desperately trying too follow what should be a simple on but can't find any diagrams to help.
I am trying to trace the emergency brake switch wires. The switch has the light blue connector and a large gage black wire that ends on a loop terminal with bolt on the switch. The Blue wire is intact but the BLACK wire was cut at some earlier point. I cannot figure out where the black wire should go. It LOOKS like it might have gone to a plug that went to a seat or seatbelt connector....a flat gray plug....this plug has a brown wire on one terminal and a large and small black wire on the other. This plug was also cut at some point. It looks like the large black wires might have been connected together but not sure.
I just need to find the main wire that this black wire should be connected to.

Does anyone have a diagram that might show this wire/emergency brake switch? I would assume the black wire cannot be a ground since the blue wire is carrying a signal and the switch is used to complete the circuit to the instrument cluster Brake Light indicator.

oh please...help!!!
Thanks,
Ken

Yeah, my wire is light blue/white stripe. So...that black wire is an unknown at this point? It 'seems' it travels up to a flat connector that goes to the seat somewhere....and joins another black wire in the same connector pin. I'm feeling I am not going to be able to figure this one out......
Thanks for the photo though...definitely what I'm looking at.
Ken

Thank you so much for the guidance and pictures. I guess, according to this wiring diagram, I just connect the black to ground. I sure didn't want to setup another issue with my fusebox after just replacing it with all it's wires. That was a lot of work but I was finally able to get all the connectors free from the block and replaced with my good stock wires. Don't want to do it again!!!
Thanks again, you are always soooo much help! This poor 92 just might run again someday.
Ken