Fits better than my hemi, that's for sure. Though you're going to have to get custom headers and a custom oil pan. What are you doing for headers, BTW?
I commend you for the build- I think it's awesome. I'll be interested to hear how much you end up spending on the oil pan, headers, and motor mounts (I'd guess cheap if you made them, expensive if someone else did?). Hopefully what you spend there doesn't outweigh the money you saved by going with a 5.3 LSx vs a 5.7 hemi...