No build design using a dunnage rack and removing one back seat. The dunnage rack in combination with the front seat folded down forms the bed platform. A outdoor chaise lounge cushion forms the mattress.

Dunnage Rack dimensions:
Platform 48 inches x 21 inches
Front legs 10 inches
Rear Legs 9 inches
https://www.therestaurantstore.com/it...

Hangar rail 48 inches
https://www.therestaurantstore.com/it...

Mattress:
74 inches x 22 inches x 5 inches Chaise lounge cushion

https://www.wayfair.com/shopproduct...