Here is a link to a recent 300zx General Forum post:
my-budget-build-thread-you-have-to-lear ... 01452.html
I have already asked the creator of the post to explain more in depth about how he did his tuck, but the post has lots of pictures that may help you get an idea of how much work it will be. He did an AMAZING job tucking his engine bay... Hope he posts back soon as to what all he did and how he went about doing it. He even moved his power steering reservoir to some of the un-used space under the bumper.
My main question to him was whether or not you have to lengthen the wires on the harness in order to move the under-hood fuse box. Seems like it would be a big project to lengthen 30 wires by 5 feet to get them under the dash...
Good luck with your build BTW!!!