Proportioning Valve - which one?

To my recollection, the KH system did not run a P-valve. Instead they ran the safety sw/distribution block and a metering valve to the front brakes.
However, if you truly have an oem P-valve, then feel free to run it.
But it kindof goes back to tires.
I believe you understand the purpose of that valve, and how it works. Or rather how it was supposed to work on original vehicles.
Many times with modern tires, and big-N-littles the P-valve is just not necessary and just steals stopping distance. Those big-piston calipers have a lot of power. IMO the 10"drums will have a really hard time overpowering them with tires that are two or three sizes larger than the front, without a valve in there at all.Only testing will prove my opinion tho.
I wonder if you are perhaps timid to plumb in a valve at a later date, due to the chore of re-bleeding the system?
Or I suppose you are running all tires the same size; in which case I might try that oem valve............................................
Naw, I'd still try it without. If the rear is found to be too strong, I would sooner downsize the rear wheel cylinders. And that is what I did with 235frt/245 rears.
I only ran those 245s for a short time. They just were ridiculously undersized for my power level.Eventually I was able to fit 295s back there. But I left the one-size-smaller w/cs back there.