best air chucks for Ram DRW

If you want the best chuck (or best anything), don't buy Harbor Freight. That's where you go for the cheapest Chinese stuff.
This one is quality:
Snap-On

I have one similar to that Harbor Freight chuck and my built in gauge is also out. Reads about 5 psi low. Still the best dually chuck I've used though.

I use this one from Harbor Freight but found the built-in pressure gauge is off. I use my accurate digital gauge on the outside tire to get the compensation value for the HF gauge and then check the inside tire with the HF gauge compensated.

http://www.harborfreight.com/dual-chuck-tire-inflator-set-with-hose-3-pc-61380.html

using the straight head adapter and 1" valve extensions I don't have to pull caps or simulators, it works right through the holes in rim.

I had a harbor freight inflation but everything they sell is the bent head inflation, than the hose pulled off within 6 months.,

Here is a digital gauge that has the straight head.

Harbor freight also sells a decent dual head pressure gage, as do places like Amazon and Ebay.
BTW, to be able to access the inner dual you will need to remove the hub cap and wheel liner. Putting them back on is a miserable choir, and if not done right can cost you $150.00 for a new one. Dont ask me how I know.

Ditto on one with straight tip end.
You can buy them at truck stops. Sometimes for outer dually the reverse tip is hard to seat, but adding 1" valve extensions solved the problem.
I like the valve extensions as they also close fully, keeping the dirt out with no need for cap.

look for one with a straight end.
this one is called Milton MILS693

the most popular is the one where the outside end is bend, but its hard to use on our trucks. But I have steel wheels, can't see how much different they would be from yours for putting air in tires.