[G&R's57GMC]

Good place to start is seat belts . The backing under the floor should have a large plate of at least 3/16” thick and 3” round or rectangular with no sharp edges contacting the floor sheet metal .
Small window cab : Shoulder belts need the above plus the same behind the upper mount plus the panel fully welded to the rest of the ceiling panels .

Big window : The pillar should reinforced over its entire length with 3/16” plate with a nut welded to it . The entire pillar should be welded with continuous bead on all sides and into the ceiling panels .

“Bear claw” style door latches should be used to prevent the doors from opening in a collision.

Relocating the gas tank out of the cab .

Collapsible steering column and shaft from column to box .

Rear of hood pins to plenum to prevent hood from being pushed through windshield in a collision.

Adding more welds all around the cab to strengthen the entire cab .

Seats with built in belts need the mounting points in the floor reinforced like the seat belts above .

Headrests or higher seat backs . Ya ya just limo tint the back window to hide them .