To gain both height and distance you would have to somersault over it. A basic jump can give you a lot of height but even running up to the jump would still mean you waste a lot in height compared to the total distance you'd traveled forward. The flip is a way to extending the travel, it loses height but that is the trade off you have to make !
Watch almost every video where a bocker is jumping over a big object and they will flip over it, that not showing off it's the best way to do it !
So before you attempted a car you have to learn to flip, flipping in it self is a good first goal to set yourself, some would be happy with that, but you go for it
There's loads of video's of people jumping/flipping to study and learn from. There is a very good video on car jumping on this site that you may already seen and well REALLY give you a goal to aim for
http://www.pro-jump.co.uk/sitepage/ProJump-Stilts-As-Seen-On-TV.html Good luck and we all hope you make it one day and well love to see your video when you final do reach your goal !