Can I use Stunning Fist on a touch attack to deliver a spell?
An unarmed strike can be both a stunning fist attempt AND deliver a touch spell, but when doing this you must attack regular AC, not touch AC. You will get your unarmed strike damage, whatever the touch spell does AND the target will have to make the stunning fist save.
Champion of Irori eventually gets to make a standard action unarmed strike as a touch attack. That could deliver a stunning fist or a spell but you're not likely to have a decent level spell to cast by the time you get that trick.