Does your 69 have a 12 bolt 3.55 posi?

Trying to determine what motor is most likely the original for my car.  Have the original rear as described.  I know that this rear was only available with a 350 motor, and could be a 300 hp or 255 hp.  Originally a auto car, now a 4 sp. m21.  Getting this car as close to factory as possible.  Not giving up the 4 sp though.  Have an m20 with perfect stamp for the build date which is 3d.  That will go in this winter.  Have my eyes/ears open for a motor with close dates.  One gentlemen with alot of knowledge stated that this car most likely had a 300 hp motor due to the rear. 

I have a 12bolt with a 355 gear in mine although it isnt original. I know this cause I just had it built and installed.So I am curious as to how you know that one is original since there is no vin stamped on it? do you know the original owner's and the history of the car ? Are you the original owner? Or is it because it is there and the stamping's line up with the build date of the car?

I am 3rd owner of the car, and second since 1984.  The date is all I can go by beyond the prior owners info.  The car does have non-original motor/trans.  I feel it is highly unlikely that the original owner "happened" upon an exact date correct rear, or searched one out on purpose.  These cars were not being treated that way in the early 80s and before.  Obviously, anything is possible, but have to follow logic for my assumptions.

I think part of your problem is going to be that there were so many rear gear options available back then in sharp contrast to recent years where there were only one or two choices. When I bought my new Z/28 in '69 it came with a 3.73 posi rear gear, a friend got his Z/28 a few weeks later with with either 4.10 or 4.11 posi, another friend got a '69 SS 396/325 with a 2.73 posi rear, all three of these were 4 speed manual trans., I think there were something like seven different "performance" rear gears available in '69 though I may be remembering that incorrectly.
Clyde  

I have researched the optional rears via the dealer brochures from 1969.  There is a table of available drivetrain combinations.  There are only a couple of ways that a 3.55 12 bolt posi was available.  That is why I felt I could accurately determine the motor, or at least get very close.

quote:

ORIGINAL: buckmaster

Trying to determine what motor is most likely the original for my car.  Have the original rear as described.  I know that this rear was only available with a 350 motor, and could be a 300 hp or 255 hp.  Originally a auto car, now a 4 sp. m21.  Getting this car as close to factory as possible.  Not giving up the 4 sp though.  Have an m20 with perfect stamp for the build date which is 3d.  That will go in this winter.  Have my eyes/ears open for a motor with close dates.  One gentlemen with alot of knowledge stated that this car most likely had a 300 hp motor due to the rear. 

  what year is the car please ? I'll see what  I cant find out. do you have the #'s off the rear that you can post that would be very helpful

Rear has the following stamping:   BT0321 G2 E.   Car is 1969 Camaro Convertible, RS optioned X-11.  Was Floor shift auto.  Has 03D build date.  Any help appreciated.

3.55 isnt that ford

quote:

ORIGINAL: buckmaster

Rear has the following stamping:   BT0321 G2 E.   Car is 1969 Camaro Convertible, RS optioned X-11.  Was Floor shift auto.  Has 03D build date.  Any help appreciated.

BT=68 or 69 3.55:1 12 bolt Posi Unit
03=March
21=21st day of March
G=Detroit Gear and Axle Plant
2=2nd Shift
E=Eaton Posi
yes probaly original rear.. post the vin and tag #'s and we will see how eveything line's up if that is the original rear "need cowl tag info or A PIC would be outstanding and vin to be sure" which it appears to be the 350 would have been 300 hp

Cowl tag sequence is 12467NOR256XXX, vin is 6211XX, carries 711 int. code, X-11 Trim code.  Is an original RS car.  Build date code 03D.

Correction to prior post:
 
Cowl seq is 2885XX, vin 124679N6211XX.  Car is also original 79B paint code. 

Positraction rear ratios 1967: 2.73, 3.07, 3.31, 3.55, 3.73, 4.10, 4.56, 4.88. 1968: same as 1967 except add 2.56, add 3.37. 1969: same as 1968 except add 3.36, delete 3.37.
Clyde