And how did they come up with this diagnosis of mold in the vents?
Air samples taken and sent to a lab?
Are you experiencing a respiratory system reaction while in the truck?
Mold in the vents? Was the vehicle ever underwater? Salvage vehicle from Katrina maybe?
Even if the AC drain hose was blocked, you would see water on the carpets long before mold set in.
Are you sure it is mold?
I would make sure the AC drain is not partially blocked.
BTW mold hates cold, crank the AC