I was lucky to get the drawings of the bus. With the measurements it's easier to design and plan what fits where but the true measurements can only be done in the bus. Many things have been planned by just with pure feeling and luck.
There a free tools that can be used for 3D planning for the inside. Ikea provides two at their website: one for kitchen and one for bathroom. They are simply enough and easy for anyone to use.
The kitchen plan tool looks like this: https://kitchen.planner.ikea.com/fi/fi/planner/35A05375-E0B4-4401-8452-41DB0504DF9C/?ref=share&fbclid=IwY2xjawH89ltleHRuA2FlbQIxMQABHQxCbbQUAQaGWF3O7-N30rNq1WF9Far8eYJrIAyI4-W9vIBh8ELJeZXKqg_aem_JHLoxYeyqMOUhxYQfbtHmA
The bathroom plan tool looks like this: https://www.homeonwheels.guide/bathroom-plan
Design tools used in this project