Cotton tape was by far the most common tape for high end 10 speeds in the mid to late 70s. It's my understanding that various plastic tapes had been around since the 60s, and were popular at that time. I wasn't around so I can't say.

Cello tape may have been around in Italy in 1975, but it did not catch on in a big way in the US until about 1981-1982, when it was all the rage. That's when I started racing jr's, and I recall clearly. Perhaps one of the forum members who raced in the 70s can fill in whether some hipster racers used it earlier. I didn't see it around. Though I was only a kid circa late 70s, I had joined the local velo club and saw what folks were using.

Ambrosio Bike Ribbon became popular around around 1980 as well. It was, AFAIK, the first padded vinyl tape. Cinelli "cork" tape started to be used around 1984-1985. Not 70s appropriate at all.

Also, some people were using the thin 'racing' Grab-On foam grips, which are conveniently forgotten nowadays. That's what my Masi had when I got it in 1980.