Oh yeah...no problem finding the carb! You've got to be joking! Those carbs are extremely hard to find and very expensive when you do find one. Luckily, my car has the original carb. If you do find one, it will go for somewhere around $200 give or take a little. Then you need to rebuild it. A "regular" carb for a 400 can be bought for $50 give or take...
Well either you're confused or have lots of cars because in your original post you said you had a 77 Formula with T-Tops auto....now you say you've got a 77 Formula with T-Tops 4 speed. So which is it? They made 756 W72 Formula's with an automatic transmission according to John's paper....and he's pretty darn accurate. He doesn't breakdown the T-Top cars, but they would bring the number down quite a bit in my opinion.
If you have 3 second gen birds.....I'm really, really jealous. And, all are W72 cars. Save some for the rest of us.