My suggestion is what I do with the 4.56 car I put on 30inch talltruck style tires and last checked got near 1 mpg better. Example ith 3.55s I got 12 with 3.90s I got 10 with 4.30s I got 11 with 4.56s I got 12 again with the tall tires. I love to check things and see the results but Yes they do rev but why di I have it to drive it! So if you have big block use the 2.94's no question but if you have a 7.5 comp small block you need to take advantage of every trick you have and still run on mid grade or regular Anyway you look at it have fun thats the key!!!