My thoughts are, running a 216 at 65mph isn't cool, especially for long periods of time. I would suggest, if you want a highway cruiser that you change over to a full oiler 235 engine with an upgraded tranny and differential. (or keep a spare 216 handy)
The Interstate system was designed and built AFTER 1953 most cars and trucks prior to 1953 were driven on state roads at 50MPH or less.
