you can get cetane suplements for diesel fuel. maybe you should make your decision based on power to weight ratios, or maybe torque to weight ratios. if you plan to drive this car daily and take it to the track for the occasional thrill then a vw diesel is ok but if it is to be a dedicated drag racer then maybe you will want to consider a different power plant. not that a diesel vehicle can't be fast, this shows the contrary:
http://list.priceweber.com/cummins/sidewinder.html and there is the tdi gti in europe, but i think it might take a bit of work to extract big numbers from an idi diesel, but maybe i'm wrong and it just needs a higher manifold pressure and intercooler. at least the rabbit has a light body going for it. if you can manage to shoe horn a vr-6 into a rabbit that will definately get you down the track in a hurry. another thing to consider is that front drive cars are really difficult to build to drag race since the body's weight will tend to shift away from the drive wheels on a launch. once you reach a certian power level you will have a difficult time keeping traction. i'm not sure that the phrase "hook up" has ever applied.