I thin re50 came in a 350z version tho i may be rembering wrong! 96Y maybe the speed/load rating i think
Have a read of this http://www.tirerack.com/tires/tiretech/ ... ?techid=35
When you buy the RE50s or otherwise You select the speed rating sometimes and there are varients for specific models in some cases. These may have slight differences im not sure.. Maybe a marketing thing but you are normally fine.
Price wise try camskill They are normally good. I would have thought RE50A should be fine. I cant check exactly what mine say... Cars in shop!
http://www.camskill.co.uk/