WOW, 3000 rpm at 120mph... that's a great overdrive gear... my Honda civic si is at 3000 rpm at 65mph...
2.73 back end is not bad. Raise that and you will start burning gas like V8 Bronco or more LOL.
My last Mustang was a '90 5.0. It's got 11-15mpg and was not as fast as my 2007 4.0 V-6. It wasn't one of my favorite ponys. I've had 7 Mustangs, I'd rank it 6th out of the 7. The worst was a 1976 (based on the Pinto chassis).
"2.73 back end is not bad. Raise that and you will start burning gas like V8 Bronco or more LOL."
"Not bad" as long as you don't mind the increase from 6.2 seconds to 7.3 in a 0-60 run. Gas mileage was never a problem for my Mustangs. I could get into the mid 20's cruising the highway even with the larger 3.08 axle. Running around town was around 18 as long as the tires didn't have any smoke coming off of them.
I sold Ford's back in the 90's and there was a Mustang GT with the 2.73 axle on it and it was a dog. We couldn't sell it to save our lives. The Traction Lok made such a huge difference in performance and it was a no cost option on the car at the time. I wouldn't even look at a 5.0 with an "M" code axle in it. "Z" code all the way.....
I would have put the '90 at 8th out of 7th if mine was getting 11-15 mpg. Were you driving on the highway in 3rd gear? You had some major issues with your car there to get that low of a mpg rating or you were just driving it in too low of a gear consistently. You should have checked for pools of gas from your leaky tank in your driveway!!
Oh, and the 5.0 with a traction lok was faster by at least a half second to 60 over your V-6 car so in no way is the 2007 V-6 faster than a 5.0. It probably feels faster 'cause it sits lower than the older Mustang but you are shy about 15 HP and three times that much in torque. Of course if you had an AT or a 2.73 rear end it would have been closer. And if you actually had a '76 Mustang, you really only had 6 Mustangs all together.