285/65r16C - Sprinter super single, 30.5" tall, 4300 lbs payload per tire. That's beyond the rear GAWR of any SRW pickup, and within earshot of a dually.
But I'll have to agree with mkirsch, no one wants a big bad 1 ton pickup rolling on 30s so they won't market one. Works perfectly on a Euro van though.
I slapped on 235/65r16C (Ford Transit tires) on my old 2nd gen cause it's not worth re-gearing an old truck. Dinky little 27.8", but easily exceed my axle capacities. Amazing mileage and braking, but little respect from local rednecks.