Can anyone explain why the Vin plate on my 1991 130 Defender has a GVW of 3500 kgs (same as current 130) but only 1200 kgs for front axle loading and 1850 kgs for rear. Falling short by 450kgs of the permitted GVW. Current axle loadings are 1580 & 2200kgs. These figures are important as I need...