If you go with the faster (longer) pitman....definately ALSO change to the longer (C body) idler. Some say it doesn’t matter..that’s not my experience at all. I put a fast arm on my 70 Cuda and it really did screw up the Ackermann angles...you could feel it as you drove through a turn, especially a decreasing radius turn like a freeway exit,

The idler is cheap, but take that into account if you have clearance issues.