Wheels question
 

I have a 70t with both steel 15x5.5 wheels and a set of deep 6s (15x6) What were the correct tire sizes that originally came with the car for both those wheels?

Steel 165 ? 15
Fuch 185 70 15

Is this correct?

those are the original sizes. Unless you need to win Concours, you need to consider other sizes.

For the "correct sizes", you can go to Coker Tire (Coker Tire - Buy Vintage Tires and Wheels) and watch your wallet drain down. The Vredstein and Michelin are in the correct sizes and tread patterns.

If you want to just drive around, try a 195/65-15 tire. While "ultimate" performance tires are no longer available in these sizes, for street use, there are some good selections. Check Tire Rack for some choices.

I am restoring the car to concours condition. In that case are the wheel sizes different?

Check with the fellows at the Early 911S Registry BBS (Early 911S Registry) but I think your sizes are correct.

For Concours, you would need to go with the Coker Michelins.