Lately my son found an old RC car from 1984 in the dumpster. The car looked not so bad at all, only it came without remote control. Any way, we took that car with us to see what could be done. First we opened the car up, and checked if the motors still worked. They did. So we decided to throw out the old receiver, H-bridge and stuff, and replace it with some „newer“ components. Finally we ended up with a RC car controllable through a LEGO power functions IR remote controller which we hooked up to a Toshiba TB6612FNG dual H-bridge.
It has to be noted, that the LEGO IR receiver itself comes with two outputs usable to drive a motor clock- and counter-clock-wise. Thus, if you are sure, your motors are good with a 9V power supply, and that they do not draw more Amps then the LEGO receiver is able to provide (I was not able to get some numbers for that), you could directly connect the motors to the receiver. Personally I like the idea of having separate power supplies for the controller/logic and the motors. Thus, the TB6612FNG is connected to the receiver. The receiver then is powered by a 9V battery, and the motors are supplied by 4 AA batteries. We also added some nice blue LEDs which lite up whenever the car drives forward.
More information on LEGO power functions