Jeff, 

You've already checked the archives, and I hope the tire discussion in
the FAQ on the Syncro Westie page,
http://www.pipeline.com/~tforhan/swhome.htm and Ron's tire info and
links at http://www.vanagon.com were also helpful.

Since you have 15" wheels, you obviously cannot use the stock sizes,
but whatever tires you have must be capable of properly supporting the
vehicle weight. I think there are two dangers: blowouts from inadequate
tire  load ratings, and sloppy handling from low sidewall stiffness and
low tire pressure.

Look on your drivers side door jamb, or there-abouts, and you will find
the 
maximum gross weight for the vehicle, and, at least on mine, the maximum
weight per axle. Divide the max weight by 4, then the max weight for
front and rear axles by two. Pick the highest number of the three, and
lets call it 
the load requirement, the weight each of your tires need to support. 

(Another complication is that passenger tires running in light truck
[LT] applications need to have a 10% safety margin. This is not a rule
of thumb, it is a specification. So if your load requirement is, say
1300 lbs, you need LT tires with a max load of 1300 lbs, or passenger
tires with a 1430 lb rating.)

Now, on the sidewall of all tires sold in the US there should be a
maximum  load specified in pounds for a maximum psi. If the maximum load
rating of the tires on your van are lower than the load requirement you
computed from your GVW sticker, go back to the tire store and
demonstrate the fact. Tell them they recommended tires that are unsafe
for the car and you would like to work with them to find a suitable
replacement. (A friend of mine did this script recently, and the
salesman did not go for it, but the manager immediately recognized the
problem [and liability, no doubt] and gave him full credit for the
inadequate tires, though he already had 2000 miles on them) On the other
hand, if the max load number on the tire is higher than your load
requirement, you are in good shape in terms of weight carrying ability.

Now, lets go back the factory recommendations again. Look at the first
two:
185 R14C 40/48
205 R14C 36/43.

The "C" is a load rating that is not given to passenger tires, so VW is
specifying light truck tires here. Note that one of the favorite tires
of vanagon owners, the  Yoko Y356 is "D" rated, which is an even higher
load rating than factory specs.

The last tire, the 205 70R1497R (??) 36/40 is a passenger car tire, the 
R1497R is decoded as R-radial, 14 (wheel diameter) 97 (this is a
passenger 
car style load rating code, though a typical passenger car might have a
rating of 89), and the confusing second R is for "Reinforced".

Ric Golen of the list has two new sets of tires for his Syncro Westie.
One set is the BFGoodrich Radial All-Terrain T/A 27 X 8.50 R14 LT that I
also run, real meaty brutes, and the second Michelins, I believe, that
he got for long distance highway crusing. They are probably the Michelin
LTX 195/75 14 or similar. These weekend we were chatting about the two,
and while the Michelins are definately quieter, he noted that the
BFGoodrich tires handle better, presumably because of the stiffer
sidewall. 

As per differential pressure front and rear, the specs and user
experience has most people running the fronts 5-8 psi lower than the
rears. I run 45 and 50.

Good luck,

Tom F.