The first and most obvious question is why do you need a blower in a desktop machine.
Ignoring that, using the amazing power of visual guesstimation, the height of those mounting holes seem to be about the same as the tops of the enclosure. If this enclosure is 90mm (it's slightly bigger than that), there's no way that's 80mm.
The second question, is if you can build an bracket to mount it anyways, why are you worrying about what size it is?