Selling your overland vehicle in South Africa can be very complicated, the carnet and SARS South Africa both state that the selling of a vehicle under a carnet is prohibited. Although some carnet issuers allow the carnet to be transferred into another persons name others do not. It is very important that you check this out with your carnet supplier first. A word of advice if you do decide to sell, a South African will have to go through a long process to import and as they have not had the car in their name for a year will have to pay the full taxes on the registration. Another Overlander from your home country may be interested and you will have to transfer the paperwork into their own name.
If you do decide to sell please be very careful on advertising in South Africa as the local government agencies have the power to take the vehicle from you.