will 17" wheels or (rims) off of a 94 work on an 85 that has 16's on it now. they are 8.5

I posted a "link" here about the various C4 wheels/offset and back spacing a few days ago----you can use the '94--17 inch wheels however you'll need to use 0.75 (3/4 inch) spacers to get the correct clearance. I've personally never been a fan of wheel spacers myself---hopefully a member who has the later wheels on a early c4 will post a reply and tell you more as far as what they like or don't like about the change.  BTW Welcome to the forum 

thank you for your help.

The 3/4" spacer is correct and what MidAmerica Motorworks sells as a kit.  I am looking at 17 inch wheels with Hoosier 275-40-17 R6 tires for competition and those who have gone that route recommend a 1-inch spacer due to the larger width of the race rubber.