I believe the torque converters are different between LT1's and LS1's but are the 4L60e Transmissions interchangeable other than that?

I have a line on a James Lovelady "built" 4l60e supposedly capable of 700Hp for $900

I unfortunately don't know enough about the builder, or transmission to know if this is a descent idea or not. Unfortunately I can not get a list of parts that was upgraded as the transmission is in secondary hands.