ive recently changed the standard gearing on my a10 (with a 356 cam so slightly more hp than std, hopefully) by fitting a 22 tooth engine sprocket instead of the standard 21 tooth, the reason is that I wanted a more relaxed engine at 100km ph, its actually not made much difference to the cruising and it still seems to me to be revving a bit high, and it has meant more changes up into 3rd up hill it previously would do in top, so I would say gearing up is of marginal benefit for new zealand roads, so bsa got it more or less right. I definitely would not gear up more eg to 23 tooth.
Just my 2 cents worth!