Though I agree as an H code Mach 1 this should be a 9 inch. But for consideration one thing you can look at is the pinion snubber bracket welded to the floor transition between main floor and trunk area. If there is no snubber and appears there never was one installed that would point to an original 9 inch. The 9 inch has the snubber mounted to the pinion cover itself and bounces into the floor pan bracket vs the 8 inch having the bumper actually mounted to the floor bracket. So to be clear again both would have that same bracket on the floor pan just one uses it to mount the rubber snubber to and the other as a point for the snubber to bounce into.
My car is also a DAP built H code Mach 1 built June 10 just in front of yours. It has a 3.00 in a 9 inch.
