[RichardJ]

OK, you provided the link, but did you read or fully understand what the guy was trying to tell you?
Actually, it really isn't your fault. The guy did a piss-poor job of what he was attempting to explain.

He was clear about one thing. Everything, anyone sees connected to a brake system is immediately, INCORRECTLY labeled as a proportioning valve.

The item you have there is a Metering Valve. It also goes by the name, Hold-off Valve. It connects to the front brake system only, but after the Warning switch.

The article was trying to explain that in 1967, disc brake systems used several different and separate devises to make the brakes work properly.

In addition to the Dual MC they used a Differential Pressure Warning Switch PLUS Metering Valve PLUS a Proportioning Valve. Three different items with different jobs to perform.

Your first picture has a Dual MC sitting on top of a Pressure Warning Switch and a Metering Valve. You still need a Proportioning valve.

The article also explains that the three items were replaced with a Combination Valve in most cars by 1970.

The non-adjustable, standalone Proportioning Valve were usually mounted on the frame near the rear of the car. Not sure why. Chrysler used the same valve and also mounted it near the rear. Most people don't know it's there or what it is.

A Combination Valve would include everything you need.

Wilwood sells an adjustable Proportion Valve, that includes the Switch. Add your Metering Valve to the Wilwood and you have a complete system