73 LCA shaft, Does it have to be pressed in?

[WH23G3G]

I'm using red Engergy Suspension urethane bushings for the lower control arm. I know I've read a bunch of B-body front suspension rebuild articles and know that the LCA urethane bushing can be pushed in by hand, since the outer shell stays in the arm. But what about the shaft with the inner sleeve? I've got the bushing in the LCA and now I need to put the shaft in. It still has the inner sleeve on the shaft, but I can't quite push it in by hand. I know I've read articles where they're using plain rubber bushings and the shaft has to be pressed in. Do you have to do that with urethane? Oh yeah I still haven't totally figured out how this suspension system works, but even with the urethane bushings, how come the old inner sleeve is retained instead of putting a new one in? I guess I can't picture now, but doesn't that inner sleeve have to move with the shaft, it looks like it's always welded itself to every shaft I've taken off.