Wife wants a 64-66 'Stang...

My wife has wanted a classic Mustang for years.. and I promised I'd get her one for her 40th birthday,.. which is still 2 years away, but I want to start gathering info/data now so I can keep an active eye out for the 'right' car for her.. I'm currently working on restifying my own project car ('71 Dodge Dart), so I also need to complete that within the next 2 years before getting her a Mustang.

So, I don't know much about classic Mustangs (personally, I prefer the '69 bodystyle, but this car is for her ) .. so I don't know what options/engines/transmissions/rearends were available in what years, don't know the weak points, etc .. looking for some guidance.

here's what I know..

She prefers the early body styles, 1964.5 through 1966 (was '67 different?)
She doesn't want high performance
She wants an automatic
She would really like A/C (was this an option back then?)

So, I know I'm looking for one with a straight six, automatic... now, is A/C even realistic? can it be found?

Any problems with these engines or the drivetrain that's associated with them? should I look for a V8 even though she prefers not to have one? I figured I could keep the cost down by finding a 6 cylinder...

Did they have front disc brakes back then?

Thanks for the help..

Also, any other places to keep an eye out besides Craigslist and ebay?

thanks guys.. I know the fastbacks are more $$ .. and while I know she would LOVE one of those, I (and she) understand that a coupe is a more affordable (and easier to find) way to go, and she's cool with that too.. I hadn't considered Cars.com.. I'll have to check it out