I'm mainly a bus guy so I'll take the liberty of chiming in. you're absolutely right that stiff tires make a huge difference in van handling.
LT tires will work, Load range C is "6 ply rating" OK if greater than 1500 lb load rating. less than that is generally not safe
best tires for a stock bus or vanagon are 195 or 185R14C (no middle number, C here is suffix commercial/reinforced sidewall) all of these are rated at 1800-2000 lb rating (97+), Load Range D.
there are only a few manufacturers of 185R14C, Michelins are super expensive, Wynstar Phaser is a chinese michelin good value, Hankook RA08 is what I have run in the past, currently using the Continental VancoWinter from TireRack, they also have a few other Continental Vanco tires. Yokohama makes the Y356 but it is not M+S rated. Vredestein makes a summer (non M+S) and a winter tire as well super stiff at about $100 ea. Probably best bet if you can find the Hankooks locally, it's a good tire.