That's true. P30's came in a variety of GVWR's. A good way to tell is by how many lugs they have on the wheels. 8 lugs are 10,500-12,300; 10 lugs are for 14,500-16,000. Also, if for some odd reason the GVWR isn't listed, you can find it (a range) by decoding the VIN.
Mine is a 10,500 and I'm afraid that it may have exceeded the capacity by how it rides when it's full. I've noticed most food trucks are around 12,000 to 14,000.