This is pretty weak, but:

In one thread someone mentioned there is a write up about installing newer gauges (tach/speedo) on an older GS. I've used the search function, but can't seem to find anything related. I'm about to pick up a post 2001 set of gauges, but don't want to get in over my head with necessary modifications to make them work (I'm already way in over my head!) Will this work? Thanks in advance.

The speedometer should be fine, I don't think that changed. The tachometer changed from mechanical to electric at some point. If you get an electronic tach, it will be a pain to make work on your bike.

Gotcha. Thanks for the reply. Guess I'll just go with the Trail Tech Vapor that I was originally going to get...   

Just so you know, not only does the trialtech not take a mechanical speedo input, nor does it take a mechanical tachometer input. SO basically if you didn't want the hassle of using the 2001+ gauges, then going to the the trailtech is even more work.

Why not just find a tachometer and speedo from a 89-00?

Right, I didn't think it would be that much of a hassle. For the speedometer, I just put the magnet sensor on the wheel, and for the tach, wrap the wire around the spark plug. I guess I'll need to plug the tach hole in the motor, but as far as I know, beyond that there is no additional work. Is this going to be more of a hassle than I think?

I remember Jay_Wolf - and maybe somebody else here - going digital on his old GS, AFAIK it was a Vapor (?) and I don't recall any issues in installing it.
BTW, any tach '89 to '03 will fit. 2004 saw the introduction of some changes in the GS lineup, among which the F model and an electronic tachometer.
Speedometer...I suppose any year would do, the only change I'm aware of is the graphics, which were updated in '01. And, of course, mind the units (km/h - mph).

Good luck

It Was a Acewell unit . no it wasnt hard to install . just epoxyed a magnet to the rim ,and had a sensor mounted on the fork leg , and that was the speedo, and it was just a wire that wrapped round the coil ,. and it took the revs off that , i had it mounted with a standerd rev counter to check how accuarate it was ,i think i had it round 3 times , and it was more or less spot on

Oh dude , i believe it was 2002 when they switched to the digital tach , or it was 2004 ,. either way , u can use a set of 2001 on a older gs , it will fit straight away , i have a set on my Gs500 on a Kat Front End

Sweet stuff! Thanks for the replies, guys! 

The 02 has a mechanical tach, no 03 in US, 04 GS-F started electric tach.