Teddy,
I did chop my body mounts, but it was more because of the wheels I got and the offset. If you are lifted 3" up front, with normal offset wheels, you should be fine to not do any chopping.
As for mileage, after 33K miles on the tires I have been getting around 18-19 mpg. They still ride quiet, and I have been doing the 5 tire rotation every 3 to 5K.
Hope that helps.
Jay