Being that I have the 2006 Tacoma V-6 and 2003 Ford F250 both in my driveway now (and big insurance bill to match ;-) I must defend the Tacoma's towing capacity in some situations. This fall (pre-F250 days) I took the Tacoma and a 24' tandem axle car hauler with a steel bed, unloaded weight ~3500-4000#, out to a farm auction east of ABQ. We had to drive through the mts E of ABQ on I40, then out and north. We loaded a windmill tower, two large windmill heads/fans/etc, plus alot of tractor parts on the trailer. I'm guessing we were at around 5000# trailer+load. The Tacoma pulled it with no problem. Freeway merging and maintaining speed and braking wasn't an issue. (Have a Prodigy brake controller.) The trailer load was "low", and had no wind resistance.
The Airstreams are all around 10' tall, and 8' wide, and have a larger profile. Although my
Sovereign is less weight than the windmill load, it feels quite abit different towing. The Tacoma has to work harder pulling the higher profile AS than the car trailer with a low-load. So I don't think the towing weight is the only thing to consider when looking at the overall setup.