I almost went with MT-10, but it brings the spellcasting power 1 up over the original.
The cleric class would cast at 13th, giving it 7th level spells. Still, by the book it would be okay. Maybe define a defensive spell for that level?
Next question would be:
According to the conversion guidelines, we can only use what's in the SRD. Can we stat the Kuo-Toans and Mind Flayers? Or do we just say see page xx of the Monster Manual?