Iuse a
Hitec HS-5625MG servo in my SCX10. It was something Ihad leftover from another vehicle. Most of my other RC vehicles have Savox servos. There are a lot of good choices on the market. The Hitec Iuse could actually be more powerful for crawling purposes. A servo with torque in the high 100s or maybe over 200 oz/in would be a good choice. Speed isn't as critical. Where you start to run into trouble is when you install high powered servos that draw a lot of current from the ESC. Sometimes you have to run a separate BEC or install a capacitor so the ESC doesn't clip when you steer.
My brother has a Wraith soI can ask him if he found any good mods for it. Ihave seen plenty of aluminum uprgrades like axle housings, linkages and other chassis components. You've probably seen them at RC4WD.