I debated this very issue on my last 540 inch street Hemi build. I have mostly had iron blocks, but have had 1 aluminum Hemi block that was in a Dart and have helped buddies with their aluminum engines.

I went with the iron this time for two simple reasons: First, I have had a few issues getting aluminum to seal. Never had those problems with any iron blocks. Second, I sometimes jump on it before it is fully warmed up. Not a real issue with iron, but could be in certain circumstances with aluminum. For a less experienced builder like myself, the iron was just less likely to cause me an issue.

Then there's the fact that 150lbs or so on the nose is not a big issue for my application.

You guys with more building experience and different uses may not have those issues. But they could have been for me.