EVLEE,
Looked through the AC Propulsion site! Sure looks like you are on the right path to have the right power to go for the Class I record. The AC Propulsion system is very neat! and I'll bet (you are probably already talking to them about this) that if you tell them that it is for a world speed record and the length of time that the system will really be working is only a few minutes they will gladly let you run the thing at 50% more power. The great thing about this type of drive is that if you can keep it cool you can really flog out some HPs!
Looking at the weight of the system you end up with about 80kgs for the drive and the motor which leaves you 420 kg for the rest of the car. What are you estimating your battery weight at? If you are really crafty you might be able to get the body, chassis, wheels/tires, transmission etc in the 250 to 300 kg area which could leave you 170 kg for batteries. Plus with a 500 kg limit you need to have a very aero shape as you cannot add ballast to gain traction. Actually with the AC system I'll bet you could get the Class II record.
Neat project except the $25,000 price tag on the AC Propulsion drive system is a little stout.
Keep us informed!!!
Rex