I have read this thread over and over and I just have to through my 2 bits in.
firstly, I firmly beleive 90 % of the fuel economy concerns are driver induced, if you drive around town at 4000rpm...you will get crappy fuel economy. and you deserve it.
if, as said by others, you build a sensible build, overdrive etc you can get decent fuel economy. and you can have fun doing it.
performance and efficiency are not mutually exclusive. The idea of building a performance engine is to increase the efficiency, air and fuel in effectively = volumetric efficiency. Your right foot controls the fuel flow. having the power and using it ALL the time are two different things.
I commute 135km per day.
I have an Escape V-6(wanted 4x4 for the winter) 30 mpg
97 Taurus SHO 30mpg
09 GT500 30 mpg (highway cruise set)
65 fastback 347 with T-5 .63 od 27mpg
all of them get way worse when I drive fast
And "Hack" hit the nail on the head, with the 40 year old car comment regarding carbon footprint of new cars, we ARE recycling!!!!!!
sorry to be so long winded