I know I'm gonna be told to do a search on this but I have and could not find the exact information I am looking for. I am working on getting the paint and body work along w/ a set of wheels done on my 1991 Z28 as soon as I get out of the hospital. I have decided to go w/ an 18/20 combo to get the look I desire but I am unsure if the size I am thinking about will work. So first off will these sizes work on my car w/ this backspacing:

Wheel Size Rear Spacing Bolt Circle Hub Bore I.D.
Front 18 x 9.5 5" 5 x 4-3/4" 3.187"
Rear 20 x 9.5 5" 5 x 4-3/4" 3.187"

If this will not work the wheels I am looking at also offer a 5 1/2" & 6" rear spacing so just let me know what you might think is best. Also please let me know if you think the rear tires will stick out from the side b/c I do not want this at all. Thanks everybody for your help in advance.

 

what type of ride height are we talking?

 

I have a Tokico Complete Suspesion Package (Springs, Struts, and Shocks) on the car giving it about a 1 " - 1 1/4" lower than factory ride heigth. I added this when I completely rebuilt the entire suspension less than a year ago w/ All Polyurethane Bushings, Motor & Transmission Mount - Lakewood Trailing Arms & Panhard Rod - Edelbrock Torque Arm & Strut Tower Brace - Wonder Bar - 36mm Front Sway Bar - 24mm Rear Sway Bar - and alot more ......

 

alright so your not going for a jaw dropping aggressive stance then which means you should have no problem fitting the norm.

assuming your going cast wheel which is evident by your half sizing your best bet would be to measure keeping all upgrades in mind. 9.5 wide up front is wide indeed but can work

i run 18x8 4.75 and 18x10 6.75 for me it's perfect but i have a much different suspension and outlook on the car. best bet is to mock up and measure your setup yourself.