Sounds to me like you'll be wanting to do the following additional Mods (if it isn't already on your to-do list) for that Crawler you crave:
- Extra gears in the Gearbox:
http://www.gcrossett.com/zipzaps/mod...slow/index.htm
- Weigh the wheels down:
If you've got spare copper wire, wrap a bunch around the inner wheels and then put the tires on.
- Swap in a faster/torquier steering motor:
I hear a lot of recommendations for swapping in a ZipZaps Red motor.
Good luck!