For such a lite trailer. A diesel is just over kill. Yes it has higher main cost. But it also has much higher cost up front. Plus your diesel comes in a 2500, or 3500 truck. both are larger, and less manageable than a 1500. Meaning harder to park, and maneuver.
You want a GMC./ Foe me a much better choice than it twin Chevy. Same truck, GMC just looks better.
You ask about the rear gear. Get a 3.73, and the largest V8 GM offers, and you will be fine. A 24' 6000lb TT, is perfect for a 1500 GMC with the 5.3, and 3.73 rear gear. Also look at the GVWR. Nothing under 7000lbs
