I have a buddy that installed black grandsport wheels 17 by 11 in the rear but in order for it to work he had to install adapters wich i dont trust at all, is there a company that makes the black zr1 in 17 by 11 that would work on a 1991 z without the adapter???

 

Not that I know of. The spacers are not bad, as long as you get the kind that have studs on them. This way, the spacer bolts to the rotor, then the wheel bolts to the spacer. My friend had to do the same thing in order to use late model mustang bullet wheels on his 66 stang. We've taken hard turns at 60-70mph in that thing, and the spacers are still holding fine. Hehe, probably the only downside is the fact that afterwards, your car will have 40 lug nuts... :P

 

You can invest in a 4th gen rear which would eliminate the need for a spacer.
You will need to do some hammering though since they still won't fit perfect. Here are some shots of me test fitting my friends GS wheels onto my 86 T/A,




And since it was dark and raining, I didn't feel like banging in the rear fender and moving the bump stop, I just grabbed a 2.25" spacer and bolted that to my 4th gen rear and then put the wheel on to see what it looked like.
Stuck out too much,