this topic has been covered plenty in other threads.
but long reply short:
without mods, you probably will stick with a 120/70 in the front. and yes tkc80 is fair for the front only. 10000km is very possible. less aggressive choice is the shinko 705.
the rear tire choices are more flexible. 150/70, 170/60 also fit. I personally will try a 170/60 next, because more rubber, and the intended 60% profile is likely to handle and wear more correctly. I would NOT put tkc80 on the rear (too soft), I would never put a K60 scout again (13000km, but no grip). I did 9000km with a anakee wild, a bit short lived but amazing grip in all direction. I'm on the shinko 805 now, too early to tell anything, I didn't put it for mileage but for mud/rocks grip. Here too a less aggressive option is the shink705. Lots of good opinions about the old mitas e07 but it is discontinued, only the new e07plus is offered here and the reviews for mileage are not as shiny as the old version. The Tchecks caught up with programmed obsolescence...