Proportioning Valve - which one?

George
That is nothing more than the Safety switch and distribution block. Leave it there and plumb it in. If one end of your system develops a leak, the plunger inside will move over and ground the sw, which will then turn on your parking brake lite, telling you, well if you see it, that something is amiss. There is nothing else going on inside it. I would leave it alone. Plumbing is exactly as before.
If you are gonna run same size tires all around, and if you have an oem P-valve, which looks similar but larger,you can swap it in there, and again the plumbing remains the same.That is the easiest, simplest,quickest,cheapest,and is almost guaranteed to work.