I had a '70 400 bolted up to the '77 T/A I bought. I'm pretty sure the Pontiac block had two different sets of bolt holes cast into the block for different motor mounts so the factory could use the motor in a variety of cars, just by changing motor mounts. if you use the T/A motor mounts, they should bolt right up and fit. So, my answer would be yes... only question i would have is about the deck height of the intake, to allow the shaker to fit right. I have a '70 intake on mine now, but i'm using the Edelbrock carb, so my fitment for the shaker is a whole nother story..... if you can get the depths of the 69 intake vs a '77 intake, you will have your complete answer......
oh...... and the '70 400 that was in it came from a "B" platform car...... Catalina, Bonneville........Executive....