cpsqlrwn

I am venturing into an area I know nothing about. I have my eye on a mid 80's Trek 400 triple at my LBS. The bike is in decent shape and has Reynolds 531 tubing and has 6 speed indexed downtube shifters. I want to keep the bike a triple (no compact crank suggestions please) and I am considering upgrading the bike to at least 8 speed and perhaps 9 speed which will provide better gearing options in the mountains, while using indexed shifters on the downtube. This is going to be an inclement weather, winter salt on the roads bike, but I still want to use decent components. I use Campy exclusively on all my bikes, but this bike I am choosing to go a different route. I am looking for suggestions, guidance, wisdom, experience, etc. on what brand and group to use. Thanks for any help, etc!

Zaphod Beeblebrox 

You might run into spacing issues trying to squeeze 9speeds into dropouts made for 6. Being that its Steel you should be able to spring it open and make it fit if you really want.

When I hear Rain, Inclement Weather and Road Salt my mind immediately thinks "Internal Geared Hub". SRAM makes a bunch of good ones and I think they just came out with a Bar-end mount for their shifters...that way you could use your Shifter bosses as Cable stops.

If you go the Derailleur route you might consider a Shimano MTB derailleur like the Deore XT as it was likely designed with grit and mud in mind or Suntour Cyclone MK II would probably look good and be period correct on that frame.

cuda2k

I'd say go with a Shimano Deore or XT derailleurs from the early 90's, 8sp cassettes are still fairly easy to come across in mountain gearing, and wheel options are still plentiful for the most part as well. Indexed shifting to allow for more concentration on the road during bad conditions.