Ahhh 4:10's with the 5 speed.
My '01 with 3:54's and 6 speed has a life time average (190,000 miles) of 17. 6 mpg. I've had annual averages of 18. 5 mpg for the last 3 years.
I'm stock accept for 4" exhaust (with free flow muffler and resonator).
Life time single tank high was 23 mpg and low was 10. 2 (towing 8000# down I75 on the west coast of Florida, 102 deg F, 80-85 mph to keep up with traffic).
The scary thing about maintaining records like this is you see all the money and fuel you've used. I'm over 11,800 gallons for fuel that I paid nearly $22,500 for.