It’s always tricky when brands start changing their box sizes. Here’s what I’d do: use two 3.9-ounce boxes of instant pudding mix in place of the 3.4-ounce size. Since you’re using a little more pudding mix overall, I recommend adding about 1 to 2 extra tablespoons of milk to keep the filling smooth and creamy — not too thick.

So instead of exactly 2 cups, try using 2 cups plus 1–2 tablespoons of milk. That small adjustment will balance the extra thickening from the pudding mix and give you a great texture for the pie filling. Please note that I haven’t tested this, but I think it should work.

It is 2, 3.4 ounce boxes of instant pudding.

No, this will not work correctly. I would try to find the instant pudding packets to mix with milk.

One cup of whipped topping goes into the pie, the rest is for the top of the pie. You can add more to the top if you like, but the recipe only uses 8 total ounces.