Okay, let's try this again
Since the tank is only 40" long, I'm going to say NO to most tangs with the exception of a Yellow, Kole, Scopus, Tomini, Bristletooth or Convict. You could probably stretch to get a Purple Tang in there, but I wouldn't recommend it.
1 Kole Tang (or one of the others I listed above)
1 Yellow Tang (or one of the others listed)
2 Dwarf Angels (or similar fish - yeah they'll fight in the beginning, but they usually get over themselves, mine did)
2 Clownfish
3-5 Anthias (I prefer Lyretails, seem to be the easiest/hardiest but there are many others)
3 Cardinals or other schooling fish as mentioned in other post
2 Gobies (you could even do three, I have 2 YWG and a Sleeper Banded)
1 Blenny
1 or 2 smaller wrasses
Mandarin
The options are endless, I just prefer more smaller fish zipping around than a few larger fish. I would stay away from most larger fish because of the length of the tank.