The following plots, kindly provided by 2woody, show the effects on gearing of an Omega with the available diff and gearbox options:

http://images.omegaowners.com/images/faq/GearingInfo/image001.gif

http://images.omegaowners.com/images/faq/GearingInfo/image002.gif

http://images.omegaowners.com/images/faq/GearingInfo/image003.gif

http://images.omegaowners.com/images/faq/GearingInfo/image004.gif

http://images.omegaowners.com/images/faq/GearingInfo/image005.gif

http://images.omegaowners.com/images/faq/GearingInfo/image006.gif

http://images.omegaowners.com/images/faq/GearingInfo/image007.gif

http://images.omegaowners.com/images/faq/GearingInfo/image008.gif

Plots are of road speed in MPH along the X axis against engine speed in RPM on the Y axis in the available gears.