To connect the dots with what John et al said. If filling through the shifter base:
Remove the fill plug first. As you fill through the shifter, keep an eye on the fill plug on the side of the trans. When fluid starts to come out the fill plug, the trans is full (assuming you are on level ground, etc).
Fox T5's take 2.7 qts, and I dont see how yours are different (though the input shaft is longer, the box is the same dimensionally, I would think).