oh you are swapping the upper control arms.

just slide the torsion bars in the LCA when the upper arms are unbolted.
make sure the adjusters are the screwed all the way out so they are loose in the arm. the LCA will rotate down until it touches the K-member.

from there, you should be able to rotate down torsion bar pivot blade in the LCA by hand, that makes it easy to align the hexes on the bar and LCA socket.
if they are hard to rotate then I would also loosen the bolts on LCA pivot pin to make it easier.

The torsion bars don't really have a front/rear, but i install them so i can see the part number at the torsion bar crossmember.

once the torsion bars are starting to slide in the arms, the hexes are aligned and all that, i use a piece of wood in the rear of the bar, tap it with a hammer to slide the bars into the sockets.
I also clean the sockets out and put a some fresh clean grease in there.