53/39 didn’t come into use until the 80s. 39 was not possible with the Campy NR crank and 144 BCD. Only when the 130 BCD came about, thanks Shimano, did 39s get used. And the 53 was usually not the high end. Most folks ran a 52 with a 14 and later a 13.
How did we get up hills ? There are hills that I ride now that I passed by earlier years because they were just too steep. First year I rode the Mt Washington Hill Climb with my 42 21, there was some walking. Next year, I borrowed the huge fw from by sister’s Raleigh Record. It might have had a 26. Whatever it was, the ride was so much easier that year.