I've got 3.23's and 20% OD... about the same as 2.76 with a 1:1 top gear. It works great. It cruises at around 2700@75 MPH. RPM is actually higher than it needs to be for cruising but its nice to have plenty of reserve power without downshift. As posted above, it depends on the combo. This in an E with 496 and moderately big cam (243@.050).