If you have the Class 2 hitch you can upgrade to a Class 3/4 with an aftermarket setup but keep in mind your trans cooling capacity, light wiring and tow weight capabilty.
CLASS I TRAILER HITCHES
- Class I tow hitches are weight carrying (WC) hitches rated up to 2000 lbs. gross trailer weight (GTW) with a maximum trailer tongue weight (TW) of 200 lbs.
- A Class I hitch usually has a
1-1/4" square receiver opening.
- A higher class drawbar does not increase the towing capacity of the hitch.
- Class I hitches usually attach to the bumper, truck pan or vehicle frame.
CLASS II TRAILER HITCHES
- Class II hitches are weight carrying (WC) hitches rated up to 3500 lbs. gross trailer weight (GTW) with a maximum trailer tongue weight (TW) of 300 lbs.
- A Class II tow hitch usually has a
1-1/4" square receiver opening.
- A higher class drawbar does not increase the towing capacity of the hitch.
- Class II hitches usually attach to the bumper or vehicle frame.
CLASS III TRAILER HITCHES
- Class III hitches are weight carrying (WC) and also are weight distributing (WD) depending on the vehicle and hitch specifications.
- Not all Class III hitches are rated to be both. See the specific hitch for that information.
- Class III hitches used as weight carrying are rated up to 6000 lbs. gross trailer weight (GTW) with a maximum trailer tongue weight (TW) of 600 lbs.
- Class III hitches used for weight distributing are rated up to 10,000 lbs. gross trailer weight (GTW) with a maximum trailer tongue weight (TW) of 1000 lbs.
- A Class III hitch usually has a
2" square receiver opening.
- A higher class drawbar does not increase the towing capacity of the hitch. To use this class of hitch for weight distribution requires a weight distribution system.
- Class III hitches attach to the vehicle frame only.
Credit to http://www.usa-trailer-hitches.com/hitchclasses.htm for hitch classifications and specs.