One thing you can say is if you can power brake it to 2200 your stall speed is higher than that. Probably not much higher because of the relatively low torque output of the 300. Most cars won't allow you to get too close to the actual stall speed because the brakes give way. That rear looks like the factory one. Gears might be limited. Maybe check in on the driveline forum. Somebody might have a better idea. Usually if you go into the "4's" the carrier has to be changed. Maybe you can find some 3.90's. If you can't get better gears than a higher stall is all you can do. A nice 10" unit would do.
