I am tinkering with a 55 GMC very similar to the first truck I owned. I am still in the trucking business. Back in the 50's we didn't pay any attention to manufacturers ratings. Sometime during the 60's Texas raised the maximum gross weight from 72,000 to 80,000. I put a Newway drag axle under the old gmc and hauled 58,000 pounds of grain. With our trucks of today we legal less. The old gmc with an aluminium trailer weighed 22000 and now we consider ourselves light at 24000. I am going to try to get the old thing looking like something first and then do the mechanicals later.