IMO - I'd stay aluminum. Although the extra bore of an LQ4 gets you into some wicked awesome heads, and probably will be cheaper overall.
...I don't know, I'm torn in my own post.
May make sense to cost out rebuilding vs crate. Price is probably going to be better overall on an LQ build, not to mention once you go to the 4" bore you can get some real awesome heads. It's something I've thought about doing on my truck (06 Avalanche 1500) many times...