The reason they sell those with the bushing and ball joint already installed is because most shops have NO luck swapping them in the original LCA.
I've done a LOT of work on Nissans of that era, and I can assure you, there's no money to be saved. I've bent a couple LCAs trying to press out the BJ, and the bushing shell is equally a PITA (due to the shape of the LCA - it'll crush the arm before the bushing budges). They can be burned out, but the shell still has to come out (which can be cut, but by then, you've spent all day on it). Then you bend the LCA putting the new bushing in.
BTW, do both of them, because if one's bad, the other is right behind it. It's a small investment to do it right.
Tension rod bushings are (I'm almost 100% sure) the same as 300ZX and S14. Easy swap.
I'm gonna let the J faithful chime in, but I could have sworn the Z32 or S14 LCAs were a direct fit on the J30. I'd be tempted to order one just to see!