[Barry_R]

While a 428 is a darn good lower cost alternative, there is no way that a comparable condition 428 block is anywhere near as good as the 427 block. It's not even close. The 428 will split 100 horsepower sooner, it'll have a smaller bore by at least .100", and it will not add as much value to the car.

So - in terms of durability, power potential, or value the 427 is the better pick. In terms of usable power and fun per dollar spent the 428 (and for that matter a 390) is a very viable option.

The aftermarket FE blocks are better than any of the factory stuff by a wide margin. The Genesis block is visually identical to an OE piece externally (I can even fix the only easy to spot item...). If I were building an FE Cobra I would either run a stroked 390 for the economics, or a full out Genesis or pond based 427....