I would visit ORRA and see what people are running locally. It helps to have support with spare parts too after all
What I do know... the speeds at ORRA can be pretty high, so use a motor with a good amount of power and make sure there is room to add a cooling fan close to the motor, if needed.
Also, check out the 'Te koop/Gezocht' topic (
link) - It's a topic for all trade activity in the Belgian sub-forum. Once you know what car you'd like, you might be able to get a good deal there.