1946 was indeed the first year for the 2 ton rated Chevrolet trucks. If on the ID (VIN) plate you find the first two letters "OR", "OS", "PJ", or "PK", it's a 1 1/2 ton. If you find "OE", "OF", "PV", or "PW" it's a 2 ton.
Spanky Hardy Collector Of Fine Old G.M. COE Trucks & Antique Holmes Wreckers