The best motors for this kind of application will have a pretty low Kv rating. Sometimes it's hard to find motors with a low enough Kv, that will bolt right up, or even fit at all. Some of the very low Kv motors are so large they just won't fit. The options are not as plentiful, when you want a brushless motor. Look more at the out-runner type motors, as they usually have a lower Kv rating, but not always. In-runners are traditionally easier to bolt up, but run faster.
Figure out what sort of battery pack(s) you want to run, and then figure out what motor Kv you need. In general, a motor that spins 6,000 - 8,000 rpm at full throttle will get you in the scale speed neighborhood. For example, if you want to run 12 volts, divide 6,000 rpm by 12 and that will give you the Kv rating you need. It would be about 500. If can't find a motor that comes close, then pick one that is closest, or if you can't do that plan on adding an auxilliary gear reduction or reduction box to a faster motor. You'll need to calculate the motor speed, based on the reduction, so you end up with a good scale speed.
Current really isn't something you'll need to worry about with a truck. Most trucks are geared so low, you won't even come close to maxing out a brushless motor or brushless ESC.
Turns is more for brushed motors, as brushless motors use Kv ratings more often, but sometimes they use both. I would rather watch the Kv rating, rather then turns, simply because not all motors of the same turns run the same Kv rating.
If you need some examples of brushless motors you can run, check out these -
http://holmeshobbies.com/home.php?cat=19
I am sure there are others out there, but many require some modifications to bolt up like a 540 or 550 can motor. Most will not just bolt up. Many have larger motor shafts too. So standard pinions don't fit.
Is it worth the hassle? Maybe. Most scale trucks are not power hungry. Most brushed set-ups run smoother and offer better throttle control then brushless set-ups. Sometimes brushless systems feel like an on/off switch at the especially slow speeds. Sensored brushless systems are closer to brushed low speed throttle control, but I still think brushed motors give better, smoother response.