Ring and pinion ratio’s are almost always overlooked as a performance upgrade. Most late model performance cars are still required to eak out the most gas mileage possible. The car can really give up performance to get less that one mile per gallon better.
A proper ring and pinion upgrade can feel like a 50hp gain and a minimal loss of MPG. It can be a very cost effective way to “add” power to your seat of the pants feel. On a classic era car it was common to use a “highway gear” because there was no common overdrive transmissions. Now when we swap an overdrive into a classic AND set up a proper sporty ring and pinion ratio, its quicker around town and runs less RPM on highway, best of both worlds!