B4 and GTB 6.5??

[Sensory Overload]

First off, congrats to everyone for making this such a great site. I only wish we had tracks like yours here in Canada.
As the title suggests, I have an extra GTB w/6.5 motor and was hoping to use it in my B4 next year. I'm told that the 7.5 motor is a better choice (by a few local racers) and that the 6.5 is way, way to much motor. Its funny that the same 6.5 in my Kyosho Lazer is truly outstanding, I just don't see why the change to 2wd would make such a big difference on the motor selection. Any help / gear ratios, etc, would be wonderful. Sensory Overload