i don't think it is a 428 this motor is not external balanced. it is hard for me to believe it is a 390. i saw time slip for this car it ran 12.33 when it had 4.11 rear end gears. is it possible it could be 390 block with different crank combination ? just not sure. i have not seem a 390 with the ribs on block ? I am a Chevrolet guy this is my first ford i just have never had such a hard time trying to identify a motor. yes block doe's have 352 on LH front of block. thanks for input FFR428