dtz28

I wasn't sure where to post this but I need some assistance. A guy I work with has some '91 ZR1 rims he will sell, 17x9.5 in the front (fits no problem) 17x11 in the back, 53mm ofset, first will these fit on my 98 z28, and second, what is a fair price to off this guy? The fronts have 90% tread on them but I will have to replace the back tires, I was thinkin $350-$400 is a good price since brand new ZR1s are goin for around $800 w/no rubber, and I don't want to insult the guy. He baby's his vette and the rims are in great shape. Any advice would be nice....