I've had good luck with the Hot Bodies car, and they should have one with a few cool updates coming out soon. Otherwise, I've had success with an older one from a while now, including an electric truggy conversion.
Oh, and you can run a LiFe pack without a regulator. Fully Peaked up, they have a max voltage of 7.2 volts, which is about where a 5-cell NiMH pack is at when it comes off the charger. I've been using the Reedy LiFe reciever pack with standard JR servos without problems.
Also, the 7955s aren't really rated for use with LiPo, its the 7954 that's a high voltage servo.