Dodge Dakotas came with a wide variety of differential ratios. 3:92:1, 3.55:1, 3.21:1. I could not find any ratios that Dodge lists for the Dakota with lower numberic ratios. In the past, in some vehicles, lower numeric ratios have been used, such as 2.73:1, etc.
Most mechanics will turn the driveshaft and count the revolutions of both wheels, do the calculations and select the closest actual ratio available. I strongly suspect your differential is not a 2:1 ratio.
More importantly, putting an electric motor coupled directly to the drive train bypasses the safety of having a clutch or a transmission as a disconnect. So if your electrics fail to break the current to the motor, you do not have any safety of being able to disconnect the motor. You will go for a full throttle ride, usually resulting in a very serious accident. At Pioneer, we ONLY build the "direct motor to drivetrain" configuration for drag racing where the losses in the transmission or clutch are important, and where the weight must be kept at an absolute minimum. ALL conversions we build for the street have a transmission and/or a clutch.