Clutch disc diameter?
or see if you can identify the trim/options
looks like you car could be "L" or "J" if yours is "J" whatever that means it at least had a 9 1/4 when it left the factory
if its an L and was a Europe assembled car we often got "special" equipment.. don't know why probably local environment or different servicing routine specified
look at barracudas many got high end trim and the formula S suspension and brakes i.e stuff optioned in just for export (CKD) Kit assembled or exported US assembled cars.
if in doubt get the 9 1/4 i doubt it will make much difference for this application and will work with both pressure plate
70.8 square inches of plate both sides vs 67.2 both sides
141.6 vs 134.4
6% reduction
Is your motor still producing 100% of the torque and power it made on day 1? 500-1000 miles after day one :) when it was run in.
Dave