I was at that game; it was my freshman year at Michigan. I believe those scoreboards were around for quite a while after that as well. I don't remember them changing during my time at Michigan (graduated in '71).
You have to remember that in 1963 or 4, Navy was the #2 team in the country. Roger Staubach quarterbacked them. It really was another era; Navy was a very good football team.
And 72,000 in attendance seems about right for that time period. Michigan drew big crowds, but didn't sell out very many games. Usually the sellouts were MSU and OSU. Ron Johnson was definitely a campus hero, but that was the era that Michigan students used to shrug and acknowledge MSU as the "football school."
It seemed as though the campus didn't get fired up for football the way they are now until late in the 1968 season, when Michigan went into the OSU game with a chance to go to the Rose Bowl, and came up woefully short.
Also part of that era-no freshman were allowed to play. The big schools could afford freshman teams, and that changed when the smaller schools that couldn't afford to have a freshman team in addition to a varsity team pressured the NCAA for changes.