I had a quite similar problem and it turned out I had unknowingly installed a subframe assembly with crash damage. The place where the LCA bolts on the subframe was tweaked backwards by about 3/4". You wouldn't notice if you weren't looking for it, but it becomes obvious when comparing both sides. I was going crazy thinking I had installed a radius rod from the wrong car, or something, or that my LCA was weird, but nope it was just that the subframe was placing the LCA in the wrong location.
Luckily I still have my old subframe (it just has rust, which is why I swapped it), but I was in a hurry because I needed to move and just needed to turn the shell into a roller so I could tow the car to its new home. So what I ended up doing instead of swapping the subframe back was to install just 1/2 of an Energy Suspension bushing; with half of the poly removed I could pull the LCA forward enough to also bolt the radius rod. (I don't recommend you do that! It just gives an idea how ability to bolt the radius rod on partly depends on ability to squish/twist that LCA to subframe bushing. I suppose a really stiff or misaligned stock bushing could also present a problem!)