PST advertises a fast ratio (12:1 vs. 16:1 stock)idler and pitman arm I am thinking of getting for my 70 Cuda. I have also seen fast ratio steering boxes available. Any reasons I should not go with the cheaper idler/pitman combo? Car is a 70 Cuda small block with power steering.

The fast ratio for the T/As & AARs was all done in the pitman arm.

I'm thinking about the arms for my Challenger, it looks like the way

to go.

there are these fast radio pieces for 73 and lates B bodies ?

Fast ratio boxes refers to manual steering, unless it's the new Delphi based unit for amazing money. There is an old thread in the handling forum on them. I'm not seeing a box for a 70 Cuda on their site so I dunno.

The arms are cheaper but they can hit headers not designed for the added length of the arms.

I did that swap back in the late 80's and really didn't like it. The factory T/A AAR power steering boxes that used the longer arms for a quicker ratio also had internal stops in the box to limit the travel. The box would only turn enough to match full lock with the quicker linkage and then stop cold.

With a regular box it just keeps trying to steer even when the ball joint/knuckle hits its stop. There is a lot of assist in the power box and it would just continue to steer by flexing the chassis when the steering ran against the linkage stops.

The box would flex the chassis so easily you could barely feel when the knuckles reached full travel and the chassis just began to flex until all of the existing travel in a stock steering box is deployed. To me it just didn't feel correct.

The factory power ratio really isn't too slow; to me it seems about perfect. I think Firm Feel can build you a box with the internal stops to match the reduced arc required with the longer steering arm. As mentioned, the longer arms will often interfere with the exhaust.
-dulcich