Hi, Eric.
Southern ordered its Train Masters with the intention of running them in the middle of multiple unit consists, primarily along the Rat Hole, a line so named for its many tunnels. The Southern's units possessed some readily identifiable characteristics. Most notable were lowered pilot decks which better matched the height of walkways of other units in the consist and a "Tunnel Motor" style radiator cooling array at the end of the long hood as an attempt to reduce the risk of overheating due to the excessive heat associated with the tunnels. Even still, modifications were still required due to heat buildup.
Initially, consists were configured F7-TM-F7. Later consists of SD24-TM-SD24 were employed. Southern's TMs were set up for short hood forward operation and the bell was located at the top of the short hood. I haven't seen a Lionel model in person I couldn't speak from first hand experience so I thought the best thing to do would be to provide you with some of the major features to look for. I believe the picture in your post was of a catalog illustration and being aware of the possible differences between it and the production piece, I didn't want to base an evaluation around that.
I hope this helps.
Bob