I'll have to find the pitman arm I have an see what it fits on, but one thing I do know is the 73 up power steering box is not the same as a 72 power steering box on the output as I changed the pwer steering box in my dads 72 Duster twister back in the early 80's with a box I purchased directly from a dealer and I had to replace the pitman arm , idler arm and the centerlink to use it.

I looked at rockauto and they show the same part number idler not matter what engine size you choose , but I take rockauto reference with a grain of salt as they list gas engine shocks for the 2nd gen Dodges with a Cummins engine.