It is the tall riders who have a hard time finding a suitable bike. Most FS frames are small for the marked size. I believe a small would fit you. Still, any bike does need size tuning if you want it perfect. This can be done with adjustments alone, but sometimes some parts need to be replaced when the rider has strict requirements. Crank levers and handlebar/stem are the parts that are replaced most often. Sometimes we need to cut the handlebar and seat post, or choose a different saddle. Your cockpit can be tuned with a pretty wide range of adjustment, on MTB styles of bikes especially, enough to make the wheelbase a matter of preference rather than a bike size requirement. I can tune for myself from M to XL comfortably, and my preference for longer frames is about stability, not size.