Originally Posted by
Spore
A372 addendum: I agree with exelsiax here. Your caster level is not the thing in question here, but your wizard level, which doubles as caster level (if for some reason your CL dropped for a spell).
Furthermore you CAN upgrade the item regardless, you just get a DC increase of 5 for not meeting the caster level requirement:
So if you pick the creation feat, you can substitute your cleric caster level. If you do not pick the creation feat, you do not meet (most) CL requirements and thus add 5 to your DC.
(But honestly just learn Crafter's Fortune from a scroll to boost your DC by 5.)