Just came across this video where build with a mini split ac / heat pump with compressor mounted inside van. Clever use of max fan on rear door to exhaust air for compressor.
Looks like he used a 9k btu heat pump.
senville.com
Looks like he used a 9k btu heat pump.

9000 BTU Mini Split Air Conditioner - Heat Pump - SENL/09CD/110V
The Senville 9000 BTU Mini Split Air Conditioner and Heat Pump is an efficient and eco-friendly solution for year-round climate control in spaces up to 450 sq. ft.
