This is the valve off of a 71 duster it is marked 171-0 K/H I used it with single piston brakes from a 73. It was for 4 piston brakes. it worked great
Then I have one on the brown Duster. That came from a original 71 Demon. marked 272-1 That is is marked 272-1 It does not have the K/H
Then I have two loose that I found. One is from a 70 Duster 340. marked 099-0 K/H
The other is marked 151-3 With no K/H
This is off of a 73 Duster
Notice they are different in styles but only the 70's are K/H They have the shorter adapter then the 71 and 73 which have the line around the adapter.
I have more I will check them for years and design. I believe they all can be used on either 4 piston or single piston. There is one thing I can tell you is that these two valves work far better then the cars that come with dual valves. When stopping at 100 mph plus. I don't no why but the car squats even. It seams as though the front brakes are not doing all the stopping. It also does not push applying the brakes in a turn as the older dual valves did on my early 340 69 and back cars. Back in the 70's I drove these cars like I stole them. The dual valves worked better on the heavier models. Not on the A-bodies.
Personally I would look to get one of these single valves. I use them on everything. Unless you are looking for brakes on a OEM trailer queen
Now this is only my opinion from experience from my younger day's when I drove like a nut. I am more calmed down now then I was.