1968 axle Stamps. a couple of questions

[Stewie]

I am trying to ascertain what axle ratio I have in my car.  It is a 1968 Coupe that came with the L30 code and Powerglide.  I checked the axle stamp and it is as follows  B b  0102G2.   It is a ten bollt. 
What I am asking is when you refer to BB code in your table you show it as BB  mine is B b with a non capital letter.  I know this possibly a siilly questions but is it the 256 rear.  Also in the chart it shows as being a posi rear end  and you show that there would be another letter on a second line.  Mine has non.
I know It could have any gear set but my feeling was that it was either a 307, 273, or 256.
I don't want to open it up because it is working just fine.  I am only trying to find out because I am looking to upgrade the cam.  It currently has a Turbo 400 and not the powerglide.
Thanks for any help.
I took another look and it is a G2 on the end not CS as I first had
Brian

[Stewie]

I guess I should have addressed this to Kurt.  He is probably busy.

[tom]

A rough way to id the ratio without opening the cover is to mark the driveshaft, and a rear wheel rotate the wheel one revolution while you count the turns of the driveshaft. number of driveshaft revolutions will be approximately your ratio. If you do have posi this is easy on a lift or jack stands. If it's an open diff, make sure both wheels are turning forward together, you may need a helper on the other side.

Tom

[Stewie]

I did that to make sure my last Z was a 373 rear end.  I know how to do that but I just wanted to know about the codes.  This car has had 15 owners so who knows what went on with it.   I have the Canadian GM documentation so I am pretty sure this is the original 10 bolt. What is inside who knows.

[Mark]

Probably a BP code which is also a 10 bolt 2.56 axle but is not a posi axle.  Maybe the P is in upside down.

[bertfam]

Post a picture Brian.

Ed

[Stewie]

The unit is on the car and I had to get the numbers using a flashlight and a mirror.
I don't think I can get a picture.  The upside down P seems plausible.  It is that or a lower case b.  I originally thought the G was a C and the 2 was an S.  I went to the bare metal and It is plain as day.  I will try to get a pic using the mirror.

[KurtS]

I agree, I'd have to see a pic.
But the axle code shouldn't require a mirror to get a pic. A jack is helpful.....