I also use passenger tires on my Vanagon. The first set I bought lasted 10 years, I just replaced the rears as they showed some slight cracking in the tread area. The fronts were still fine. I switched the fronts (Sears Superguard GT 44psi) to the rear and put 2 new Mastercraft tires on the front. All tires are 215/70-14 on alloys.
I would not use passenger tires on a Westy but mine is an ordinary Vanagon and 95% of the time I'm the only occupant. The tires are easily rated ok for this weight. I also never travel at high speeds, my normal max speed is usually 55-60.
By the way my local Firestone charged me $60 to mount/balance the two tires!
I was amazed that balancing is now $13.99 per wheel. They charge for mounting, balancing, valves, rotation, tire disposal, shop supplies and
 tax.

-David