Tyre size???

Hi just bought a set of Image Rs7's for my berg cup build. Car is a 83 gti and would like to get tires the same rolling radius or close as to original. The wheels are 15s, 8inch fronts and 10.5 rears. Tried a few calculators but got a few different results any input would be great thanks in advance.

Did the 83 come with 13's or 14's mucker?

13 inch alloys it states on sticker in boot so proberbly came with tarantula wheels.

195/50/15 or 185/55/15 are factory rolling radius for mk1, just need to work from there to get tyres suited for your wider rims