If you want another, you will need at least a couple data points to ID something similar.
First you'll need RPM: Get the RPM on the output shaft of the motor,. Count the rotations of your spit per minute, multiplied by the gear ratio of the sprockets in you chain drive (if any difference). If you have access to a photo sensor-style tach, that would be straightforward way to measure also.
Second motor strength: In this case the only thing that we can really go on is amp draw, which isn't a perfect way to measure motor strength, but should get pretty close. With the motor connected to the spit, load the motor up to max load you'd expect it to see when you have a hog on there and measure the amp draw of the motor.
Going to Grainger, or some other parts house, find a similar RPM and gearbox configuration and select the next highest amp draw to what you measured. That should get you close enough.
Jake