Have a look at the following site:
http://www.connactivity.com/~kgross/FAQ/944faq13.html
It lists what I believe to be all the "stock" wheel sizes and offsets for 924/944/968 series.
Keep in mind the from '86 to '87 there was a change in wheel offsets from "early" to "late" so you'll need to look for a set of early wheels.
It looks like the '86 turbo ran 7 and 8 x 16s. I think they would fit N/A cars as well. I made the same change on my '87 S, going from 15 to 16" Phone Dials and Dish Wheels (which if memory servers me right are 8.5 wide), using 225/50 front and 245/45 rear tires. No issues with fit. But remember, mine was an '87 late offset.
I sure someone on the board has done it and can confirm it works.
Marc