Well guys, this has been an interesting revision of a post I put up over a year ago as a bit of a joke, but it's taken on a whole new life. It was never mean to be serious and even I have added to it with some serious stuff.
However, the bottom line is; do we really care that much about milage, or more about "smilage". For sure gas is not cheap anymore and to those of us on (very) fixed incomes, we do drive our Mustangs a bit less, but boy, when we do, who the hell cares.
Well, it all depends on what kind of driving you want to do. For the drag guys or the Friday night car show crowd, mileage may not be the point. I have a different set of considerations that keep me from planning a hp build. I like to drive my cars, not a little bit, but a lot.
Every year I drive up to Springfield (IL, but does it matter? I think everyone has Springfield 2 hours away!) for the Route 66 festival. Once in the Opel, but lately in the 08 GT. I would love to drive the 71 up there someday. Then again, KC, Chicago, Indianapolis, Memphis, Nashville, etc. are all within a 5 hour drive. So, building for a comfortable 6 hour drive at modern highway speeds (80+) with A/C and not draining the tank every 2 hours sounds great to me. And not being deaf when I get there!
As mentioned in the 351C Build topic, the 89 GT was a 3500lb car and got low 20s on the highway. Probably at the tested 55mph, but not a bad target. With a 13gal tank (the Opel has a 13 gal, the Safari van had/has a 17 gal/27gal, both of those and the 08 GT tend to average 20mpg. I think the 71 has 17gal?), that just gets me to Chicago.
The AOD and the T5 have steeper 1st gears than the old C4/C6, so even 3.00 or 3.25 will feel a little more perky.
Of course the old 5.0 was fuel injected, but build for decent low rpm torque (not that a stock M-code doesnt already beat the 5.0 on that point), smaller carb, and all the other 'efficiency' tricks and it may balance out depending on the right foot. All the stuff Spike talked about.
My 71 is a standard sportsroof with the 351 4v, power steering, power brakes, a/c, so it may be a couple hundred pounds less than a fully optioned Mach or Grande. 3200-3300lbs? With headers, aluminum intake, aluminum wheels, maybe another 100lbs less.
Keep weight and rpm down, intake manifold vacuum high and stay behind a semi....and enjoy hours of driving, not quick sprints around the block or up to the Qwiki-Mart where you don't get to enjoy all the high performance parts!
My opinion....your mileage may vary!
