For AC versions the very first TMCC used and LCRU. It was a single board with the R2LC and the motor drive section all one. This was used on early Steam and Diesels like the GP-9 with pulmore motors. Rather quickly Lionel moved to the component set up with a mother board and the R2LC (radio), a ACDR or DCDR (Motor drive) and the RailSounds boards. The very first LCRU used RS 2.5 which was also a single combined board. After the switch to the R2LC, the RS became 2 piece also to plug into the mother board.
Your dash 8 probably had a r2lc. G