I don’t know if it will fit but IMO it’s too big anyway. That’s over 27 inches. I am running a 205 65 15 which is about 25.5″, about the diameter of the original 15″ option. The 13″ rims ran even smaller tires. The side wall on a 205 75 is going to be very high and it will roll a lot resulting in poor handling. More like a small truck tire. Of course the large diam also effects your gearing. Check out a calculator on line and you will see how it changes your gearing. Your backspacing is okay I think but might be moving the wheel in a little too much. Lots of info on tires and wheels in the forum. Use the search all the way at the bottom of the page to do some searches.
I can tell you from first-hand information that 205/70-14 on 6″ wheels fit. I can also tell you first-hand that 215/60-15s on stock 15″ wheels fit. Both of those combos are about 25.25″ in diameter. Your 205/75-15s are about 27.1″ in diameter. Those would be a good choice for a 1968-72 Cutlass, but are waaaay too tall for the 61-63 cars.
The stock tire size on 62 Jetfires and convertibles was 7.00 x 13, which was 25.8″ diameter. The fact that some vendor (who is not Oldsmobile) claims that 180/85-13 is the replacement tire doesn’t mean that it’s correct or even the same size as original.
Thanks for the replies.
215/60r15 is the size preferred. Problem is, I haven’t found narrow whitewalls in this size except Cooker and other vintage tire suppliers and am reluctant to pay $200-$300 per tire
Really should be running 6.5″ or wider rim for 215 tires. Bulging side wall will result in poor handling with a lot of side wall roll, poor steering response … 205 is about it for 6″ rims. People do run wide tires on skinny rims but you sacrifice proper performance.