Vintage Cars: 1964 Impala Convertible, full size chevy, power options

Question
How rare is power seats, power windows, and AC on these cars.

Answer
I don't know where you'd be able to find the exact numbers, but the power options were relatively rare on any 1964 full-size Chevy, maybe 10-15%.  A/C was EXTREMELY rare on any convertible in 1964, regardless of model; I'd say maybe 5%.  Put the two together, and I'll bet you'd could count on both hands the number of '64s like this that still exist.  It's the existence of the A/C that makes the care so rare- the power options are just icing on the cake.