I suggest a prewar Lionel, Ives or AF transformer with a Lionel 081 rheostat for speed control. They tend to have a higher range of available voltages than the postwar transformers. Many prewar locos will run better with 20 to 25 volts. A KW gives you only 20. I've got a 262 motor for sale. I'll test it tomorrow and see what it needs. I'm using a Type A for testing my older motors. It puts out 24 volts.
Don't get an RW or 1033 for prewar locos - only 19 or 16 volts.