7 1/4 Posi??????

7 1/4 rear was available as open or SG. early SG's were clutch, later ones were cone. I'm not sure of the year break. Clutch types are more desirable, as they have 4 spider gears, and the cone types only had two. 3.91 ratio was available from the factory in some year new vehicles. From the Direct Connection Program you could get 4.11, 4.56, 4.88, 513 gears. I have been told a 5.38 was also available, but have never see one, or seen documentation for one. I just sold a 3.91 SG unit. I totally rebuilt it after removing the 5.13 gears. The big problem with 7 1/4 rears is parts are made of unobtanium. It took me several years to find all the parts.
PS: These rears are stronger than most people think. I ran a 7 1/4 3.91 SG in my 66 Cuda street/strip car for about 5 years. 3250 lbs, 170 slant six with nitrous, 904 with a 8 inch converter and slicks. Car ran low 13's and would 60 ft at 1.81