Can you post some pics of how your current setup looks? Like Vegas69 was indicating, Tire rack's website has alot of tire data to help you choose.Be aware also, that every tire size has a standard fit rim size to go with it and changing the rim width even 1/2" + or - will change the tires footprint width about 1/4".
Paul
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1973 Z28 Street-touring project.........
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