I have made the same mistakes.
I have the k60 rear. I do not recommend the k60. Longevity sounds good but you obviously want some grip, likely for trail, mud and such and you will be terribly disappointed by the continuous strip on the rear. Skids like crazy, no grip. I think it only felt useful in the sand because it can sink in and the sides can finally work.
I have the k73 in front. It's ok in packed dirt but essentially no better than a road tire in more demanding situation. Furthermore, the continuous gap in the center acts insane on steel bridges (the grid falls in and jerks the handlebar all over when gripping its way out) and line-scarified pavement/concrete. I will definitely NOT put one again.
My next pair will likely be a shinko 705 (or tkc80 for plan B) (120/70 regular) in front, and a metzeller karoo 3 (or shinko 805 for plan B) (150/70) in the back.
All 4 have fit without mods. Absolutely NOT a tkc80 in the back; I need to get to the next gas station before the tire is worn...
Last edited by dddd; 04-21-2017 at 06:24 AM.