I have a 402 and want to bore it .125 to make it a 427 out of it. Anybody out there know if this is feasible? What is the maximum overbore for it? I've built several small blocks, but this big block stuff is new to me. Thanks  

Before my time, my father did this with two mild, street big blocks. So it can be done, but not with every engine. Only early big blocks (before '70) are thick enough for this, I'm afraid that a later 402 may be thinner compared to these earlier engines. Regardless of the year of the engine you really should have this block sonic-tested anyway. Then you will actually know the maximum overbore you're dealing with...