Corvette Performance - 1987 coupe

i recently bought a 87 corvette with 16x9.5 stock wheels..
i would like to know what i need to do to put on 17x9.5 on the front and 18x10.5 on the rear.
do i need spacers? all ads seem to have wheels for 1988 and newer...........help...plzzzzzzz :0)

I have seen c4's with c5 wheels on them. Not sure if they were just gm factory wheels or something made for the c4's.

This site is awesome for technical information but if you want details like this you are better off checking corvetteforum.com