Pretty simple as far as application on the Mustang. The two ear noses cones regardless of if auto or manual were all the same 65-67 . Starting in 68 there was a change in teeth on the flywheel to 164 which triggered a change in the manual trans starter nose cone to be the wider variety compared to the narrow one used on all automatic versions 65-70 . If you want the original look stay away from any marked that start with D1,D2 etc. Those starter nose cones were improved with strength gussets in the casting that are different looking on the inside and outside of the part.