I was talking with some of the older guys I talk shop with. they didn't really see it as a problem. Now, take that with a grain of salt because they are used to their big V8 motors. However, at the same time, those blocks are iron too. They bore and stoke the hell out of those motors. It being iron doesn't really have anything to do with it, it is the amount of metal between the cylinders. Not sure what the magic number is, but from what I can tell, you ought to be just fine.
you're planning on boost right? How much?