just put a bigger front sprocket on it (if you feel like you have to) and ride it. don't worry about needing another gear. your bike can handle the interstate speeds and then some for extended periods. I do it all the time.
If your gonna do something, do it right!
Have you considered the other option?
Get a new wife.
Love That One PG!
All due respects to the Poster, on another Post you also asked about converting a 79 to an XR type motor because you landed the 79 Free, we are entering the Dream world here, Nothing Cheap or Free in that arena and there is only so much that can be done that makes sense either in reality or from the pocket book..