70 chevelle ss raley wheeels

[P.J.]

My 70 chevelle was built the 3rd week of November 1969
my build sheet says that AO wheels were used on the car.
My questions is when did YA wheels begin to be installed on the 70 chevelles and Ao wheels dicontinued for the 70 chevelle.

The reason I am asking for this information is because Ihave a set of YA wheels dated 11 69.
So why were AO wheels installed instead of YA wheels??
and could the build sheet say AO wheels and YA wheels installed.
PJ