The 1969 - 390GT - A/T car takes a Autolite 4300 carb with 1.25 venturi at 600 cfm. Factory #C9ZF-F.
You can get one from PonyCarbs. Here is what they told me.
We can provide a factory original carb. for Core $160 + standard restoration $269.50 + shipping. Concours plating (very highly recomended) is $100 more.