Joe:

My 69 442 has a type 0 differential. It's at the body shop getting finishing touches. I don't know if it's a 10 or 12 bolt. If it's a 12 bolt, is it possible to put on a W-27 diff cover? Did Oldsmobile make 442's in 1969 with that type of cover on the Type O? My car is a numbers matching 400 automatic. I still have the quadrajet, but replaced it with an Edelbrock carburetor. Other than that, it's all original including the interior. The paint is burgundy mist with a black interior and black convertible top. It's going to be done in 10 days! Thanks! Rich Byers rbyers00@yahoo.com

 

Welcome aboard

I don't think Joe is up yet, But the W-27 was not a 69 option. I didn't become avaliable til 70

 

Type O has a 12 bolt cover, and only 10 on the ring gear, so technically, it is a 10 bolt.
The W-27 cover will fit. Is it really worth 120 bucks for an incorrect part though?

 

Welcome to CO. Tell us about your car...

 

They make W-27 covers to fit type "O", 12 bolt Chevy, and later corporate 8.5". Be sure to confirm you have "O" because each is specific. Nice appearance addition that was a dealer installed accessory or available over the parts counter back in the day. Technically not available until '70 but absolutely correct accessory for the car. Holds all or the better part of an extra quart of fluid FWIW. Get one & put it on if you like it, they look nice.

 

I will nit-pic here because we use terminology here that fails us miserably. I believe J is right on the money here with word "correct". "Correct" is best used to describe a part that is the same as would come on the car originally, be it an old original part or NOS or reproduction.
Thus in this case, the cover (no matter how cool) is *not* correct for the car.