I believe your rear end originally came from a 1975 Pontiac X body car, Ventura?
Date code: F115
F = June
11 = Day of month
5 = last digit of year, 1975
Axle ratio and Plant code: GBG1241
GB = 2.73 axle ratio
G = Chevrolet Gear and Axle plant
124 = 124th day of year
1 = day shift
3 letter (XXX) axle ratio/plant code format began in 1971, so that's why date code points to 1975 not 1965.
GB never shows up as a 2nd Gen camaro axle ratio code. It does show up on this Pontiac listing. (Look at 1975 axle ratio codes)
http://ronspontiacpage.com/reference-pages/rearendcodes.htm.Unsure whether you have a 7.5 or 8.5 in rear end. Apparently both were used depending upon the engine used.
Hope this helps, good luck on your build.
