Back-up your Interface and WTF folders before making any changes!
Interface and WTF folders go in your Classic folder. Make sure to edit the sub-folders in WTF, so they match your account, server, and character names. I'm running the game in 1920x1080. If you're at a different resolution or aspect ratio, expect everything to be all messed up.
To make setup a bit easier, I went through and added a "Port UI" profile to most of the mods, but I might have missed a couple. Aside from that, I'm not a modder, so if you have any issues you're on your own.
One note: I use a pair of macros with /details hide and /detail show to control the damage/threat meter visibility.