We did something similar to an old Ford my grandpa bought from a rollover. After some serious inspection by a local shop, the frame, engine, trans, etc were deemed straight and good to continue. We basically swapped hood and cab from newer truck to replace crushed cab, and prepped it for a dump body. Then sent it off to an outfitter that built and installed a forage box with scissor hoist. Once truck was completed, my grandpa called Michigan State Police who then came out, inspected vehicle and titles (chassis and cab titles), and issued a new VIN number for the 'new' truck. This was late 90s, right around 2000. The MSP issues a new VIN and some paperwork, SOS took both titles and MSP paperwork and created a new title for the truck. We ran it another 17 years until rust jacking destroyed the frame and it wasn't deemed worth repairing. Swapped the box and hoist to a newer truck and life goes on.