The ones on ebay look to be the 85-88 Maxima brackets they are flat and thicker and need to be trimmed down (machined to be used)
You can order them through Nissan at $100 a piece.
I tried the junkyard in my area found (1) maxima it was an 81; I believe. The brackets were there, but they were welded on. Apparently, only certain years or certain Maximas period came with bolt on brackets and not welded. If you can't find a pair I would order them from here they work with the 280zx calipers and are only $165 for a set. And they are already cut to avoid removing the stub axel.
http://www.modern-motorsports.com/catalog/product_info.php?cPath=60_61&products_id=8&PHPSESSID=27d195d4f7d45db8ddc64cd342a71765
Nissan part number for the maxima rear disc brake brackets = 44155-04S10.