This is the main connector between the engine wiring and the cab wiring. It is held together by a small bolt in the center of the connector that threads into the cab side behind the fuse panel. If you remove the bolt you can pull the connector apart and see the wiring terminals on the inside. The nut for the bolt is captured in plastic on the inside connector, and it can spin with the bolt if it is corroded. So use care when taking the bolt out. You might have to remove the fuse panel to access the nut.
These terminals are called Packard terminals and can be tricky to free up from the connector. They have a small leg on the terminal that is bent sideways so that it snaps into the connector to hold it in place. To remove it you have to bend the leg flat with the rest of the terminal to unlock it so you can pull it out of the connector. There's a thread on here that explains it with pictures if I can find it I will post it.
The wire you are showing in the top of the connector is the resistance wire from the ignition switch to the ignition coil and the cloth covering is peeled back showing the wire. This wire is not needed if you convert to HEI ignition which a lot of member do, me included.
Here is the bolt.
Here is the terminal and you can see the leg that must be bent.
