shifter

Hi all, I have an old 2004 Trek 4300 MTB (specs: https://archive.trekbikes.com/us/en/2004/trek/4300#/us/en/2004/trek/4300/details). It has Shimano drive train. I also have a Trek 2.1 road bike that I hardly use (I have a newer cannondale carbon road bike that I use, so the trek is just...