Quick question guys. 85 Camaro with 700R4 and 3.42 rear, 245/50/16

I am getting two different sizes of combonation gears I need from different sites versus doing my own calculations.

Previous owner swapped rear ends, so speedo is off.

Can someone please assist me with the proper gears I need to make my speedometer accurate?

I'm guessing the tires are 245/50/16

Im looking in my Pontiac parts book, I'm seeing
trans code /drive gear/ driven gear
85 3.42
MD8/ 15/ 41 or 42


89 3.42
MD8 / 15/ 41
MB1 / 07/ 19

The 85 also does't list 245/50/16s soo I looked at the 89s and they have the same gears listed 4 several dif sized tires..

let us know..

Tire size is in original post 245/50/16

Where the heck did you find tires that size, and why the heck would you put them on a third gen?
You need an 18 tooth drive, and a 45 tooth driven.

Corrected tire size, I misread.... sorry

According to my calculator with the corrected size I am needing 15/40..... am I correct?

TTT