1967 Ford F-100 Brake Issue Proportioning Valve?

I have tried all of the locals but cannot find this Brake Proportioning valve. It is mounted on the left frame of the truck just behind the drivers door. It is bolted on, I think I have counted 8 brake lines entering the unit and one electrical unit of some sorts.

I recently changed out the left front brake cylinder and could not break it loose. I went to the joint behind the wheel about three feet and had no luck. Each time soaking them with PB BLASTER suggested liquid from Autozone. I finally found myself back at this unit and now have rounded off the nut I do not know where to go from here. I thought if I can cut the other lines, replace this unit, and splice the other lines back it would correct the issue.

I finally cut all of the lines 5 plus one electrical sensor. I have reflaired the ends and have reattached the lines. I started bleeding the front and all went well. I went to go to the back and found that no fluid was getting to the rear cylindars no matter how many times we pumped them.

I switched the lines at the brake cylinder thinking I might had reversed them below. This did not do any good.

I have found a schematic (shown below) on a site but it is not written in a way I can understand which line goes where. I REALLY need some help. I need to get this truck back on the road. It is our second car.

ALL help is appreciated. Please email me so I can get the quickest answer.

Thanks
joe.arwood@gmail.com