The p/n for the liners for the sierra 2500 is 84496084.
Those do look correct for 2500 liners.
Procedure
Caution: Use the correct fastener in the correct location. Replacement fasteners must be the correct part number for that application. Do not use paints, lubricants, or corrosion inhibitors on fasteners, or fastener joint surfaces, unless specified. These coatings affect fastener torque and joint clamping force and may damage the fastener. Use the correct tightening sequence and specifications when installing fasteners in order to avoid damage to parts and systems. When using fasteners that are threaded directly into plastic, use extreme care not to strip the mating plastic part(s). Use hand tools only, and do not use any kind of impact or power tools. Fastener should be hand tightened, fully seated, and not stripped.
Note: U Clips come pre installed on wheel house liner assembly.
Remove the rear tire and wheel assembly. Refer to Tire and Wheel Removal and Installation in Vehicle Service Manual.
Remove the rear tire front air deflector, retain the fasteners. Refer to Rear Tire Front Air Deflector Replacement in Vehicle Service Manual.
Remove the rear pickup box paint protector, retain the fasteners. Refer to Rear Pickup Box Paint Protector Replacement
Remove the rear wheel opening molding, if equipped. Refer to Rear Wheel Opening Molding Replacement in Vehicle Service Manual.
Remove and discard the U Clips (1) at the front and rear of lower wheelhouse.
Insert the supplied push nuts (1) into the wheel house areas as shown.
Fit the wheel house liner (1) to the vehicle and install the supplied retainer (4).
Install the supplied plastic threaded nuts (3). Tighten to 2.5 N.m (22 lb in).
Install the supplied bolts (2). Tighten to 2.5 N.m (22 lb in).
Re-install the rear wheel opening molding, if equipped. Refer to Rear Wheel Opening Molding Replacement in Vehicle Service Manual.
Re-install the rear pickup box paint protector. Refer to Rear Pickup Box Paint Protector Replacement
Re-install the rear tire front air deflector. Refer to Rear Tire Front Air Deflector Replacement in Vehicle Service Manual.
Re-install the rear tire and wheel assembly. Refer to Tire and Wheel Removal and Installation in Vehicle Service Manual.
Repeat procedure for other side.