The blue alternator fan/pulley, as far as I know, was used on June and July 1965 Dearborn cars. I believe Jeff has also documented some San Jose applications, but I'm not sure what the window of production is when they were used. I don't believe your April build is applicable if you want to be correct.
As a sidenote, if you're wanting to use the blue fan/pulley to be unique, be prepared for a lot of questions and raised eyebrows with regards to the authenticity and originality of the color. Documentation like this helps
![](http://pic80.picturetrail.com/VOL847/1785303/3437215/280676342.jpg)
but there is still, probably justifiably so, skepticism. My original fan/pulley were blue, and I had a good amount of original paint on the back of the fan to match to, so I don't have a problem with it.