Well, I hate to say this and stir up continued controversy : ) but it is
fact so here goes:

I just bought a 91 Westy about a month ago.  Previous owner had some kind
of passenger tires on it called "Arizonian Touring Limited Edition."
Definitely not C rated, not anything but 1400 lbs per tire rated.  He drove
and drove with no problems.  And little old me, not knowing it was even an
issue as far as 'safety', drove over 1000 miles cross country with the new
ride at all different speeds, wind, crosswinds, rain, bumps, and had no
problems.

Now I have gotten rid of the tires, but that was first motivated because I
just didn't like them.

I tend to believe your mechanic.  Of course, the best is always better, so
to speak, but experience tells the tale.

HKS