Fantastic! Really glad you and your friends enjoyed the game.
You can definitely run a short series of Great Soul Train Robbery if you just keep adding train cars and make sure each encounter has room to breathe. An alternative approach is to run a second session with a new crew of PCs robbing a different train, but reveal that a PC from the first session (especially one who maxxed out Sinner and was damned) is the Conductor of this new train...