[fostereast]

I suspect an aluminum block out of the box has better ring seal than an NOS 427 block. The sleeves in general are much stronger due to the way they are cast and the 427 iron block starts out with pretty thin cylinder walls

If your comparing the new Genesis and Pond iron blocks to aluminum, they all (both Iron and Aluminum) have siamese cylinder bores and I bet the aluminum still wins due to its cast sleeves.

IMHO