Hi all, I have had this vintage Marin Bobcat Trail for a few years. I made it a single speed and use it for a"fitness" bike. I got the itch to put the gears back on but I don't want to use the original twist shiftier though. Is it possible to use the derailleurs and but switch out the twist shifters with thumb levers? Do I need to change the cables? I am kinda new to working on bikes. I like this bike. It's very light and in good condition and loo ks cool too.