The difference in the use of 24 and 24.5 is also in the position of the wipers as they are parked.
The windows in 58-64 were smaller and the wipers parked on the passenger side. These wiper machines used pivots marked 24.
In 65 on models the windscreen was larger and the wipers would park on the drivers side. These used the 24.5 pivots.
As a general rule, if you hold the pivot in your hand with the tip pointing away from you the pin pointing to you will be on the position the arms park to.
If you look at the wiper motor in a 58-64 it has the terminals pointing to the position they park. It is the other way round in 65 on cars. However this may be difficult to verify in cars that, over the years, had their wiper motors swapped.
The two pin pivots cannot be used between the two window types however both (24 and 24.5) single pin pivots can be interchanged.
Note the position of the wipers as they are parked in a '63.
and in a 1965...the opposite direction.
