Jeff,

You really should have 5 matching wheels and tires which you keep in a
rotation, so that they have close to equal circumference.  Otherwise, if
you have a flat, you would have very excessive VC lockup (unless you
then removed the drive shaft) and would put undue stress on the
transmission and potentially cause some parts to fail.  This even
applies to your current tires.

The need for the matching set of tires has been discussed extensively on
the Syncro lists, although there will probably be a reasonable amount of
discussion in this lists archives also.

I got my Syncro with a relatively new VW transmission in it because the
PO wouldn't listen to the dealership that kept warning him to run the
same size, manufacturer, and model of tire on his van.  He trashed the
tranny.   And all his tires were the same size, just not the same
manufacturer and model, and state of wear.

What if you have a flat, now, or even worse with the setup to which you
plan to switch?  Most of us wouldn't want to have to remove the drive
shaft and be without 4WD capability.

So, I think you need to re-figure you cost of wheel and tire purchase
and approach wheel / tire replacement with the new numbers.

--
Sam Walters

Baltimore, MD