I'm K swapping my Insight, and have put together what is possibly the tallest K series transmission ever assembled. I'll let the high level of torque take care of off-the-line acceleration and will be turning ~2200rpm (possibly less) at 70mph, hopefully allowing me to keep my 60+ mpg. Highway economy is really all about gearing and aerodynamics.
EDIT:
I'm actually less than certain about the 4.4 final drive in the EX. That's what California98Civic's Honda transmission guide says, but Honda says it can be either/or:
https://owners.honda.com/vehicles/information/2003/Civic-Coupe/specs#mid^EM2123PW