I'm using seats from a Miata on my Z as well, but my interior is a big mess right now and I only have the drivers seat in so far.
The headers were custom made by Tim240Z and I purchased his complete setup including engine, transmission, rear end, etc.
I am actually interested in possibly adding AC in the future, but I'm sure there will be installation issues and likely more cooling needed.
I don't have a wiring diagram, and I really need to get one myself:icon11: .
It's always easy to do things differently if you could do them over, but in the grand scheme of things I think I would do it the same.