Axle groupings and load limits

We have an 85 Ford L9000 that has a rust jacked frame that has split. Its a straight truck set up for hauling grain and forage. Long wheel base around 250" with a pusher set 9' in front of rear group. 20k front, 20k pusher, 40 k rears. My grandpa built the truck from a salvaged rig, state police came out, inspected and gave it a titled GVWR of 70,000.

As we are looking for a replacement, I'm also learning about vegicle configuration and load limits and wondering why so many heavy spec...

Axle groupings and load limits

Axle groupings and load limits