What size 10-Bolt do i have?

Hey guys, So im deciding to change out my 2.41 gear and maybe put 3.23 on my 79 Pontiac Bonneville. But im not sure if its a 7.5" or 8.5" Any ideas? Thanks.

 

A quick google search says it's a 8.5. If it has a 2.41 in it to use 3.23 gears a spacer and correct bolts will be needed as you will have a 2 series carrier. If it is a posi the carreir will have 410409 cast into it. Here is a bit more info. http://www.buickperformance.com/posi.htm.
Ray

 

Well i went to http://www.ringpinion.com/DiffList....&Model=Bonneville&Side=Rear&DriveType=RWDWell

And it shows it could either have a 7.5" or 8.5".

 

that is a 8.5 housing

scott

 

I went here. http://www.hemmings.com/hmn/stories/2009/03/01/hmn_feature29.html
and here at differential id. http://www.jdrace.com/.
Ray

 

8.5" by the square ears on the housing.

 

Alrighty, thanks a lot everyone.