Not all Tahoes come with them, only the Z71s or the ones that have the towing package.
I found that to be fasle. I have a 2002 LS 5.3 2wd w/o the tow package and mine has the 34" rad in it. I bought the ls1 fans about 3-4 years ago and noticed they were way too small, bbuutt they did their job very well. It just doesn't look very OEM. I found some 05 fans for 125 I'm picking up monday so I will have my ls1 fans up for cheap.
The best info I can tell you guys is to just call your local chevy lot, ask for parts, tell them you need a new radiator but not sure what size. They will ask for the last 8 digits of your VIN and they will tell you what size it is. I have a late model 02 so I call them and double check before I buy anything. Why you ask, well my 02 tahoe does not use 02 brake pads, it uses 03 pads. And when you are installing pads and after you have tried 4 different brands you start to get pissed and cuss out chevy till they tell you... Oh, sir you have a late model tahoe that's why.