I placed the meshes into the bb folder directly, yes. I don't understand the date conversation at all.
I'll try to explain it a little better...though be forewarned, I haven't had all my coffee yet.
As I'm sure you know, every file and folder on your system has a date (the day/month/year and time) it was created, and another for the last time it was changed. When Morrowind looks for what files to use in-game--meshes, textures, etc.--it's programmed to use whatever files it finds that have the
newest date attached. This means that, in normal circumstances, when given a choice between using the game's original body meshes and Better Bodies', Morrowind should always choose the ones from Better Bodies, because it has the newer date.
However...Steam's version of Morrowind complicates things slightly. As tetchy mentioned (and thanks for the clarification, btw
), the dates on all of Morrowind's vanilla/original files are bumped up to whenever you downloaded it from Steam. So, let's say you downloaded MW today. That means that all of Morrowind's .bsa files now have a date of May 14, 2010. Now...all of Better Bodies' textures and meshes have dates of 2003/2004. That means that when Morrowind goes to choose between using its original meshes or Better Bodies', because of the way it's programmed, it will always choose its original meshes--because they have the newer date.
The easiest way to fix this would be to find a file date changer (Google is your friend, or maybe someone here can recommend one in particular) and change the dates on the .bsa files. The original Morrowind .bsa should have the oldest date, followed by Tribunal, and then Bloodmoon.