How realistic you want it? You can Jbeam the whole frame like a space frame (with each beam corresponding to a tube of your frame), then jbeaming the suspension in the same fashion and you have a realistic version of your car. If you want to test just the suspension, you can consider everything apart the suspension and the engine as one piece jbeam wise, which is probably easier, but your frame will not behave realistically, especially the collisions. Everything depends on how realistic you want it
