Now were getting some where.
A 1500 HD has a 8600 GVWR 6000 RAWR with load E tires and wheels. Comes with the 6.0 engine and the tough old 4L80e tranny and can be a 3.73 or 4.10 gears. Payloads run over 3000 lbs and up to 12k tow ratings. The drivers side door post will have the GVWR/FAWR/RAWR.
If this is your truck its a much sought after 1500 truck which is the old 2500 before GM came out with the HD 9200 GVWR 3/4 ton truck.
The 1500 HD has a very light gross weight. From the factory it can have a 2600-2700 lb rear axle weight which leaves well over 3000 lb payload. I would stick with around a 2500 lb wet pin weight for this truck.
How much will it pull ?? You know it pulls your current TT with no issues.
The older 6.0 engines don't have the performance of the new 6.0 so I would stick with a 10k-11k wet weight trailer.