How can I find out what gears I have in my 69 cutlass with out taking off the cover ?it has a 12 bolt.

 

Count turns!
This has been gone over many times, try a google search on this site [not this site's search]

Basically you spin the drive shaft until you have gotten two full turns of the rear wheel[s]- this can be one turn of both wheels if you have posi, or two turns of one wheel if you have an open diff, or any combination in between. 1.5 & 0.5 or whatever.

Use the driveshaft's convenient 90 degree features to count turns to the nearest 1/4 plus or minus a little, then consult the chart of possible ratios to peg it. For example if you get just past 3 turns but not to 3&1/4 then it must be 3.08-1 ratio.

You can go for 10x as many turns if you need more accuracy- e.g. 32&1/4+ driveshaft turns to get 20 turns of one rear wheel if the ratio is 3.23 on an open diff....

 

Type O or Type C??