What is the correct tire pressure for LT265/65R17 E tires?

That sounds high for that truck. There is a tag on the door that will give you the recommended pressures for the vehicle. Many times a shop will just fill them to whatever the sidewall says is the max pressure, especially with an LT tire. The door tag will likely have a couple pressures listed, one with an empty vehicle and one for higher weight or towing. The problem with the higher pressure is that while it might give you a tine mpg increase, it also causes the tire to balloon out in the center and then you wear out the center of the tread faster as shown in the image.

https://www.2carpros.com/articles/how-car-tires-work

It's wider but still uses the same pressures. The biggest difference is that a Light Truck tire is stiffer and in reality, could take less pressure than tagged but the tagged pressure will work fine. Or just go with 32 all the way around.