Optimum static timing will vary greatly from one rig to another. Among the many factors affecting optimum static timing are compression, octane, valve adjustment and timing, carb jetting, centrifugal advance and vacuum advance/retard, smog versus desmog versus partial desmog, and others.
In general, higher elevation requires more advance. Even at sea level, the stock 7° BTDC is retarded from optimum power and mileage in order to get best emissions.
I can do 75MPH no problem on I-70 between the passes up there in a stocker. I can even stay around 45 or so going up the passes.
I am currently running about 13° on my 71 (with stock F) and about 9° in my non-USA stock 1978 (the centrifugal advance seems to be higher in that distributor). My 76 runs best at around 12°, but that was fully smogged with the original vacuum retard distributor. I haven't run it yet with the non-USA vacuum advance distributor I installed.
Here's my 25-year-proven method to best power and mileage:
First make sure everything else is in good order. Carb is jetted properly, reasonably clean (BG 44K is GREAT stuff!), no vacuum leaks, smog equipment is operating properly, valves adjusted, air cleaner is clean, etc.
Next set idle mixture and idle speed to optimal, then adjust static timing while idling (any vacuum hoses to dist are disconnected) to best RPM, readjust idle speed as needed.
The reconnect any vacuum to dist, go up biggest high speed paved hill you can find and note terminal speed. Go back down, listen for backfiring, note throttle crispness, general performance. At bottom, advance about 2° and repeat. Keep playing with it until you get best terminal speed up hill with little to no knocking, no backfiring downhill and best throttle response. Once you're there, tighten down the dist and enjoy 16 MPG and best performance. Happy cruisin'!