ez 73

I am thinking about swapping my 3 speed auto to a maxima 4 speed w/overdrive My tranny is a 3n71b. the 82-84 maxima/84-89 z31 tranny is an 4n71b Do new transmission mounts have to be fabricated? can I use the drive shaft from a z31,instead of shortening mine,can I use my existing flex plate? I understand this was covered in 2006 by " hisandherz " I couldn't find the thread. I also heard that they were talking about a 76 280z or zx I don't know if that makes any difference. Any info you could give me on this swap would be appreciated