It comes down to a mater of taste and price. Since only a hand full of us race or push our Healeys to the extreme edge, drive more than occasionally on nice days, or expect to stress the mileage warranty, almost any tire would prove acceptable. Since, it is my impression that the added adherence benefit of larger tires is questionable (I leave that justification to others), my perception is 165/80s present a longer Healey vision and 185/80s seem to shorten the image.
After determining that I wanted to stick with the 165s, tire longevity was the next factor to consider. If the available Nexens were manufactured within the reasonable present, they would have been my reasonably-priced selection. However, at the time I was purchasing (a few months back), I was told by a company representative that the available 165 USA stock was manufactured 3 or 4 years ago and I found only Vredesteins were manufactured within the year. As a result, I purchased 165/80 Vredestein Sport Classics (H-rated tires have stiffer side walls) at Euro-Tire in NJ and find them quite good.
Hope this helps,
Ray (64BJ8P1)