sometimes retiming the cam is trivial, I advanced my sohc metro cam 10 degrees with a hand drill (and some figuring).
BUT, another strategy that might help for hiway travel is to retard the intake cam, I'm not sure, but if you can "detune" the engine at hiway rpms so that it makes less power, so you can hold the throttle open more (and have less throttle lossses)
I don't think you will have any problem with 1:0.8 2.93, the thing to remember is the hp curve will probably take you to a better bsfc position with lower gearing. Hp is a function of torque and rpm so as you move left, you move up for a given power requirement, and the power requirement isn't changing because of a gearing change:
