TIMSPEED

I'm wanting to put the Weld ProStar XP's on my (soon-to-be-mine) '02 Z28. I'm trying to figure out which backspacing/offset I need to run the 16x8½'s. I wanna run a 255/50 16" all around. Thanks!
BTW: Anyone actually held a prostar XP by itself?! Things are like 5-7lbs!!

a98ws6

iTrader: (48)

Pics on my Cardomain. They are lighter than most people say. I believe that size wheel only comes in one backspacing? 5.5" I believe? If you can find the XP's great because they have been discontinued.