All 1968 Mustangs with the J-code 302 AND the GT option group had 9" rear ends. Notice I said WITH the GT option group. Standard '68s with the J-code had an 8" rear end. All '68 small block Shelbys also had a 9" rear end. The rear end in my car has never been out, the original axle tag is in place (never been off the car) and the code confirms a 9" axle with the 3.25 open gear set, which also checks with the Marti report for the car (although in truth, the Marti report does NOT differentiate 8" vs 9" for any vehicle that I am aware of). The Ford MPC lists 2 different driveshafts for the 1968 Mustang with the 302 engine. One part # for GT cars, one part # for non-GT cars. The base engine for the 1968 Mustang with the GT equipment group was the J-code 302. Optional engines that year were all big blocks for the GT, obviously then the driveshafts are different for them. In addition, I owned another '68 GT coupe, J-code with C4 back in the 1980s, early build Metuchen car. It too had 9" from the factory, but interestingly it was ordered with a 3.00 open, which was actually listed on the Marti report as an "optional axle ratio".