In terms of tire width, you have few choices with the stock 14" rims IF you
want 6 or 8 ply reinforced tires. There is only one reinforced 205 75R 14
tire available, and  no one on this list seems to have tried it. It's from a
supplier called CIP; let me know if you want the web address. Other than
that, you are limited to 185 or 195 width tires if you want to stay with
reinforced sidewall. My own tendency is to stay with the reinforced tires,
just because these vans are so much heavier than passenger cars. But as you
can see from the thread, people use passenger car tires too.

Of the available choices, Agilis seem to have the reputation of being good
but costly for what they are. I'm currently running Bridgestone 603's and
don't find any excess sway or manueverability problems with them. I'd buy
them again.

I've had great experiences with Yokohamas but not with the 356's made for
Vanagons.

There's a tire recommendation page at roadhaus.com though many of the tires
listed are no longer available.

Hope this helps a bit.