For the 737 Combi, How did changing the proportions of the passenger vs cargo areas work?
The Boeing 737QC (Quick Change) is a Boeing 737-200 which featured a 134 in × 87 in (340 cm × 221 cm) freight door just behind the cockpit. The floor was strengthened and allowed for palletized seating for faster configuration changes between cargo and passenger flights. A switch using a system designed by Falcon Aviation in Sweden allowed the seats to be removed in 20 minutes. Each seat row would roll forward to the cargo door, then slide out into a container for storage. The container would be rolled away and cargo loaded into the space where the seats used to occupy.

The video below shows how the conversion system created by Falcon worked.


                
            

Good luck creating a toy hauler.