I built a chassis mount camper on a 1953 Chevy truck in about 1968. I dropped the floor down between the frame rails in back of the differential to get headroom. and had a small over the cab storage area so it had a lower center of gravity. I solved the toilet problem by putting a hole in the floor in front of the stand up area and over the diff. Worked good, I lived in this camper in LA for 6 months. I knew all the good parking areas. Prior to my marriage and 6 week northern tour of Ca Or and Wash. Building your own camper is great fun.