I have a current customer that's using a 4L70E tranny, and it supposed to be the same case as a 4L60E. The TCI website shows the mounting point at 21 3/4" from the bellhousing face for all 4L60Es, but he measured his tranny at 24 5/16".
Too bad you can't get reliable info from these transmission suppliers. That's why I have every one of my frame customers measure their transmissions or give me the dimension they want to use for the crossmember position.