COPO F & SO number on Flint seat tag from 1969 Biscayne

[JoeC]

was the other car a 1969 Biscayne or 1968?

In 1968 you can get 4:10 4:56 and 4:88 as RPO

here is the 1968 Power Team Chart
you can see where the 1969 power team chart goes up to 3:73 but the 1968 power team chart goes up to 4:88

I have been researching this because its the same for the Novas
1968 Nova can get RPO 4:10 but in 1969 you had to get COPO 9511 to get 4:10 gears

So I think Yenko used COPO 9511 to get the 4:10 gears for the 427 Novas.

Its hard to find proof on it. You need a window sticker or factory order paperwork

I do have some Nova window strickers with COPO 9511 but not for Yenko sold cars.

I think your 1969 Biscayne would be COPO 9511 for factory 4:10 gears.

Do you have a photo of the trim tag?

Sometimes the trim tags show COPO or Special order.
May be just a dash or extra numbers or letters.

I have seen COPO or Special order police or military Biscaynes that had "MEMO" stamped on the trim tag