There are output shaft on power steering boxes are different between 70 and 74.
70 is a smaller shaft and the pitman arms are expensive.
The later boxes are a larger diameter and the pitman arms are more reasonable.
All manual boxes are the smaller diameter output shaft.
I believe you can get a fast ratio arms for both boxes. I have the PST fast ratio arms on my early small diameter power box. I also used them on my manual box in the same car.
I would be interested in selling them if you are interested. I will caution though, that a few of us, me included have had issued with some of the aftermarket fast ratio arms. There is no master spline, and the splines seem to be a tooth off. You can not center the steering wheel / box with out having different length tie rods. Not sure if that is an issue for you.
Jason