Most of us "peacefully cruise" at 65-75mph. If you do the math and your engine doesn't hiccup at the RPM that .64 and your rear+tire size equate to, then I think you'll be happy with the .64 trans. My first four gears take me up to 140mph. The
only thing I use fifth gear for is peaceful hiway cruising, and it does that quite well. But,for instance, if your 15" wheel/3.54-rear FE coughs, sputters, and bucks at 2000RPM then .64 is not right for you (unless you swap out your cam and replace it with a trusty ol' solid flat tappet
). But I'm telling you, having the ability to cruise on the hiway as quietly, and as smoothly, as if you were coasting with the engine off really enhances the overall enjoyment of owning a Cobra.