I will try and figure out exact part numbers. They are 5100s I do know that much. Bilsteins are stock for Z71. The 5100 has more travel though if you have leveled truck.
I LOVE the shocks. Money well spent.
I'm not sure what you mean be heavier load?
I used the part Bilstein recommended for my model truck 2001 Z71 Tahoe. I didn't use anything spec'ed for HD chassis.
Previous owner of my truck had put on Monroe shocks so I never got to test the stock Z71 Bilstein shocks. I can say the Bilsteins are WAY better than the Monroe shocks I replaced. I found out about 5100's because previous owner didn't have enough travel on shocks to support his leveling kit. I bought the car and first time off road ripped off the shock because was insufficient travel. I researched and found the 5100's.
UPPDATE: Here's the parts I have on my truck. Maybe different for 2004 Tahoe so double check for your year.
Ordered 2 of Bilstein 24-187237
HERE for rear of truck
Ordered 2 of Bilstein 24-186643
HERE for front of truck
Heads up Billstein now makes a version of 5100 with a reservoir system. You may like to consider it depending on what you use truck for. If I had it to do over again I'd probably have ordered these with the external reservoirs. Possibly overkill but I do do quite a bit of driving on minimum / no maintenance forest roads. I believe these shocks have similar dampening but reduce work load on shock / heat so they last longer. Somebody can correct me if I'm wrong.
Bilstein 25-187601
HERE for rear
Bilstein 25-176407
HERE for front
Double check with Bilstein parts catalog for Tahoe
HERE (again double check for your year. I looked up 2001 for my truck) You may need a different shock if you have your truck lifted / have changed suspension geometry. The parts above will support a torsen key leveling but nothing more. I honestly don't believe in lifting our trucks much more than a leveling kit if at all because makes them less streetable. Rock crawlers don't go down the highway too well