||There are 4 bolts that hold the FUCA bracket to the chassis. The FUCA is attached to this bracket by one bolt. This to me is the "inside" part of the arm, as well as the right side. You called it the left, which to me would be the outside considering we are on the drivers side.
Anyways...the other side of the FUCA bolts up to the upright which is where I think you're having the problem. I had the same issue if so,
and honestly I want to say it was on the drivers side too. Not sure if there's something up with the drivers side or if we just have bad luck...but I really had to force this side in. I ended up hitting it a bunch with a rubber mallet to get it to slide more into the upright. Getting the bolt holes to line up was really a pain but it eventually went in.
It's not gonna be easy but I think you'll get it. Just need to make sure you're coming straight on as opposed to on an angle. Good luck!