Here's the J's engine bay. You can see I have little to almost no room to even had a clutch master cylinder on the driver's side.
Regarding the suspension, from what I know, the front suspension is from a Maxima (never really confirmed), and the rear is that funky multi-link setup from a Z32. I have the Z's engine and auto tranny. Judging from the pics I've seen of the Z32 engine bay, my shock towers seem to be a bit taller up, and seem about the same width apart.
Oh, and very nice write up on your project. You have some VERY detailed information there!
Also, I've actually thought about getting a Q45 engine, but have always figured, if I'm going to go this route, then why not just drop in an LS1