Towing a 2720SD with a Tacoma V6 manual

Hi,
We just bought a Trail Manor 2720SD and are hoping to tow it
with a 2003 Tacoma V6 3.4L manual transmission 4WD extended cab.
When we bought the truck we had the dealer add the 'tow package'
to a truck on the lot. But in researching what this means since we
bought the Trail Manor we have become confused about the
actual towing capacity of the truck. The Toyota owner's manual says
3500 lbs w/o tow package and 6000 lbs with tow package. So all along
we have been assuming that having the tow package meant we were
rated at 6000 lbs.

But the dealer has now informed us that the owner's manual is talking about
a *factory-installed* tow packeage, not the *dealer-installed* package that
we have. We have been feeling like we were mislead, since no one
informed us of this distinction when we bought the truck. We knew we
were planning to use it as a tow vehicle, but the dealer did not
explain what the choices were. It is now apparent that the dealer-installed
tow package just included the hitch receiver and a 4-pin plug and wiring.

More recently, however, the service representative has told me that the
actual rating is 5000 lbs for my truck with the dealer installed tow package.
I have asked him for a published source of this number, but so far have not
had any reply. Why would it not say this in the owner's manual?
Can anyone shed light on this question?
And more to the point is this a reasonable combination? We do live in
Colorado and expect at least some of our travels to be mountainous.
Thanks for any input.
-dave