re: "...I actually dug out an old IPD catalogue, and it says you need 4 urethane bushings for the links. So I guess the upper and lower parts of the bushing are exactly the same?..."

They (upper and lower) are NOT the same.

Unfortunately, the latest IPD catalog no longer shows an exploded diagram of the car's bushings, like past catalog have shown, so I have to use analogies to try to explain them.

You need four (4) upper bushings because they're a sandwich (the bread) on top of and beneath the ends of the sway bars (the meat inside) -- one sandwich on each end of the sway bar, so two (2) sandwiches or four (4) slices of bread. Each looks somewhat like a lifesaver candy. But these are all called upper bushings even though there's a top and bottom -- they're identical, however.

And the end link goes (of course) through the sandwiches (like a toothpick in a deli sandwich).

But the bushing for the bottom of each end link (which is what I was writing about to answer your original question) is a single, cylindrical-looking bushing that goes through the "ring" (lollipop?) of the end link (and by which the end link is through-bolted to the lower A-arm).

These bushings for the bottom end of the end links is, in the Poly version, IPD Part No. 1205926-P, $9 each (you need two, one for each side).
This is different from the upper bushings, p/n 2B1020, $2.50 each, two for each side or four altogether (which should have come with the sway bars).

And like I wrote earlier, unfortunately, IPD doesn't sell new end links (if you wanted to install new ones) with poly bushings already installed -- their new end links (p/n 1206667-K, $24.95 ea.) only come with ordinary rubber bushings, so you have to remove them to replace them with the poly bushings.

I hope this helped you.