Maybe you can chime in on this, Is there any advantage to going to the larger pitman shaft box?
the boxes are the same price, but I did notice that if your buying the stock ratio pitman and idler arms, the price for the smaller arms are about double than the ones for the bigger shaft.
Yes. The bigger spines are cheaper.
The bigger shaft starts in 1973 and the aftermarket is more likely to carry and have better prices on parts for the newer cars.
Yes. The bigger spines are cheaper. 
