It's more likely that you have either the 2.56 or 2.78:1 rear as Olds did not use a 2.60 in 70. There is much debate about the "O" type rear ends. I am no expert in this arena, so I'll refer you here:
Try the Olds FAQ for more info:
http://oldsjunction.classicoldsmobil...ential%20Codes
And contact Supercars Unlimited.
www.SuperCarsUnlimited.com
Supercars Unlimited
8029 A SW 17th
Portland, OR 97219
PH: (503) 244-8249
FX: (503) 244-9639