Most of the poly strut rod bushings are made for the 73-76 style strut rods, which were longer from the threads to the shoulder to allow for the thicker later bushings. Pretty much all of the poly strut rod bushings are the wrong thickness regardless of manufacturer though. There's a lot of things to consider, you can't just make the poly bushings the same thickness as the rubber ones because the poly ones won't compress as much as the rubber ones. And of course the 67-72 bushings and strut rods were different than the 73-76. The end result though is that pretty much no one makes them the right size.
The most important part of the entire strut rod assembly is that the LCA can move freely through its range of travel without binding. Obviously the length of the strut rods has a significant effect on caster, so if the bushings are the wrong size setting the alignment can be a real problem. There is some room for adjusting the caster with the strut rods, but that ability is secondary to the free movement of the LCA.
If you want to stick with the factory strut rods and poly bushings, I would cut the poly bushings down enough to get at the threads and then install them. At that point I would check the movement of the LCA to see if there's any binding and pay careful attention to whether or not the strut rods are pushing the LCA backward. At minimum the LCA should be perpendicular to the frame, although you can usually pull them slightly forward to gain some positive caster and still have free movement of the LCA. If there's any binding of the LCA through its range of motion, you'll have to shave down the bushings accordingly as that's the only adjustment you have.
This is why I use adjustable strut rods in place of the stockers. The factory strut rods were a "one size fits most" kind of thing to begin with, and not even all cars from the factory were properly set up without binding. As long as they were close enough to get into the factory alignment spec range, they were good enough.
