Technical Dilemma: Install higher gear ratio or get an overdrive transmission?

You said it "seems like" the engine is reving high. I'd check it out with a reliable tach before I did anything. 3.08's should be just fine . I would guess you'd be turning 2K at 65mph. That's not a lot.

 

I have basically the same set up. Wind noise and all. I couldn't do a burn out on a wet road but it cruises nice at 70mph and I get 18-21 mpg and the car moves right out from a dead stop.