I traded the 8"rear end that came with the '63 parts car for this 9" back in '75. It's from a '66 K-code Mustang having the tapered tubes to accept the smaller bearings and the same U-bolts for the shock plate as the regular Mustang. The original center section was swapped out before I got this housing. I found a 4:56 gear that allowed me to get about 7-9 mpg, but it sure was fun stretching out the gears crossing a 4 lane intersection when the red light turned green. I only used 2nd and 4th gear most of the time when driving in normal traffic.
Sometime back in the late 80's I changed to a 3.70 gear when gas prices got to a ridicules price of 67 cents a gallon. The 28 spline 'WAR' case has the double vertical enforcement ribs and has the same appearance as a 'N' case. There's not much information on the web that I know of about the WAR case except that it doesn't have a drain plug on the side. Well, mine has one.
I changed the center section before the trip to the '06 FCA Nationals in Indy to a 3.25 ratio. I will be rebuilding the WAR case with a 3.50 gear ratio. The 3.70 is a little to much for long trips and the 3.25 is just no fun. I will save it for the long trips. I found a worn pinion yoke when swapping to the 3.25