It seems that dropping Concentration as a skill has also caused it to disappear from the stat block. It is still pretty important and to figure it out for yourself you need to check feats, abilities, etc. So it seems like it ought to be in the standard stat blocks.
I recommend right next to caster level.
Spells Prepared: (CL 10 ; Concentration + 20)
Well IIRC in final 'concentration checks' will now be a function of caster level and possibly key ability modifier, that would be pretty easy to figure out. CL 10, 18 int, concentration +14. Or something.