The two guys are 'Slim' & 'George' as it is Curley and Carlson who are saying the last section when looking at Slim & George walk away.
'Eating' - If "What's eating you?" you are being asked why you appear to be upset or troubled. With worries on your mind. They are 'eating' away at your calm.
And Carlson said, "Now what the hell do you think is wrong with Slim & George, they appear sad & deep in thought"And Carison said, "Now what the hell ya suppose is eatin' them two guys?"