Picture 8 from Power Shifting
Street Trucks Magazine (March, 2001)

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Each kit provides a different adapter ring designed specifically for your vehicle's transmission tail shaft configuration.  On automatic transmissions, the tail shaft is removed and the auxiliary transmission bolts between the two, even if it is equipped with an overdrive (like the Mopar 518 or 618 OD transmissions).

From StreetTrucks magazine (March, 2001)  pages 92-96
Reposted with permission from the publisher.