1968 wiper motor

Why is it that so many parts on 1968 Coronets were one year only? I have to use a 3 speed wiper motor because of the large oval air cleaner base used with the Ramcharger fresh air hood and ducting (that is why 3 speed wipers were required on most gen 2 Hemi cars). The original motor was burned up. I restored a motor, but when I went to attach the little arm to the motor, it wouldn't fit. That's when I looked up wiper motor part numbers and found a 68 three speed is a one year only motor, according to both the GG White Books, and the Interchange Manual. If you compare the first 2 pics, you can see how the threaded attachment on the first one (1968) is concentric, and the other(1969-1971) is offset. Also, it is hard to see in the pics, but the shapes of the attachments are different, so the small arms are not interchangeable, which was what told me the restored motor was different from the original. It seems to me that means the offset one will make the wipers move further. The car is not together enough to test it. I put a lot of work into restoring the motor - the insulation on the wires going from the top of the gearbox to the motor housing was gone - so I would like to use it if possible. I considered using the first gear housing, but as you can see it has a broken ear. Does anyone know if the motor I restored will work?

It may not work the eccentric allows the wiper motor to park the blades off the windscreen.

Damn....I think you need the '68 wiper motor. The only other possibility I can think of is by "some chance" the 69-71 motor/linkage would make it work on a '68...but I think that's a long shot.