I have used my Syncro to tow a parts van over 1000 miles with no problem.
Cruising was very stable @ 65 mph, although gas mileage declined to about 13
mpg (which I figure is the equivalent of 26 mpg for one van). Third gear was
used over the hills, although we did not encounter any mountains.  I say the
vans can do pretty well if you take it easy on all up and downgrades.

Budd Premack
86 Syncro, 73 Super
Minneapolis, MN (Land of Sky Blue Waters)