Where do I begin...
The 71 thru 72 had first generation Rack and Pinion, so the Rack and Cross member were different than the '73, the 73 had a one year only Rack and Cross member. The Spindles and control arms had differences for the 71-73, and mounting points were different too. I have heard that the front Frame distances between front bumper mounts differed on the 74 -80 compared to the 71-73, which is why the control arms differed and subsequent geometry with these parts. The 74 pinto was the only Pinto offered with both the 2.0L & 2.3L Fours requiring a change of Motor mounts too for any early conversions to a 2.3 L four, hence the issue of motor mounts to frame distances.
In total ,the Mini Stock parts you see in Speedway catalog , are for just that : 74-80 Pinto and Mustang II, and Kit cars using the repro subframe kits for street rods. Unless you are a fabricator, this is just a huge undertaking.
I'm sure I've overlooked the brake interchange issues with calipers too. It's why people make racers out of the 74-80 cars, rather than try to find parts to work with the early chassis.
Pintosopher,
Ridin a early one with rare parts to steer it