"What other parts are needed to finish a Doon and do you supply them?"
Assuming the chosen donor vehicle is in a relatively sound and useable condition then the only other parts that are required to complete a Doon buggy are front headlights, front indicators, rear lights and indicators, seats, wheels, tyres, rollover bar and wet weather gear.
Volksmagic can readily supply various styles of headlights and rear lights as well as having the capacity and knowledge to source and supply any other custom and performance parts required to finish your build.