Since your profile here shows a USA flag as location (Just below your alias "briankan3"), I would suggest to use MAX-BMW parts fiche to check diagrams and compatibility - prices shown in $US$. There are other BMW motorcycles part catalog on the internet, however after many years, I would say this one is the best / easiest to use:
MAX BMW Motorcycles offers an extensive BMW Motorcycle Parts fiche. OEM BMW Motorcycle Parts and Accessores can be ordered online for fast delivery. View our detailed BMW Motorcycle Parts diagrams and locate the part that you need efficiently.
shop.maxbmw.com
On the entry page above, you will see on top, in 2nd row from left , 3 memu items that will be of interest to you:
- K1200RS 98-01
- K1200RS 02-04
- K1200GT 03-04
Of course, it would take days / weeks to check every sub-pages of these 3 above to compare if they use the same diagram / assembly and same part numbers. Since I have done a lot of work on these 3 generation of models based on same basic design, I would say to always check each diagram in case of doubts - even more so when buying used parts on EBAY as vendors do not always knows all the details (these guys are parting mainly bikes from insurance).
In general, you can use these guidelines as a quick go / no-go for compatibilty:
1) all these 3 models above use the same basic engine / transmission / radiators / aluminium backbone frame (only the BLACK front and rear sub-frame have a few variations)
2) the 1st generation K1200RS has a different ABS brake system , different front brake caliper , different front rim (brake disk mounting). This also has implications that the main wire harness is a bit different (to / from ABS module).
This 1ist generation is 1998-2001 in USA --OR-- 1997-2000 in other countries.
3) All models from 2002-2005 have a VERY different and more complicated ABS brake system (a few 2005 were sold in USA but they were actually produced in 2004 at factory hence you see "-04" in list on MAX-BMW parts fiche)
4) All models from 2002-2005 have a wider and higher front nose fairing. The windshield mechanism / mounting is also different. Some came with optional wider rear rim to mount a 180/55 tire instead of 170/60 width like they had before. Some also came with optional electronic cruise-control (this will affect many other parts like handlebar switches on left)
5) The K1200GT of 2003-2004 is actually like a 2002-2004 K1200RS of the same period but with added options. Some of these options can be retrofitted to a K1200RS. Many of these options will affect other components like the main wire harness. Added features of the K1200GT were mainly:
- electric adjustable windshield (instead of mechanical 2 positons like the K1200RS)
- heated seat (not same right handlebar switches)
- cruise-control
- wider front nose fairing and also wider side fairings (they added some bolted winglets).
I probably forgot a few details, but this is getting a bit long ;-)