I started with a 500 in my M body and swapped out to a 518. OD really does make 4.10s and 27" tall tires livable. The unit I got was out of a 3/4 ton passenger van and it had lockup. Turbo Action down in Florida set me up with a very nice converter that can be used with with lockup transmissions, but it doesn't have the lockup components in it. As said, you can make OD and lockup completely automatic using the PATC parts. I sourced my stuff locally and wound up using a 52lb pressure switch to engage OD. It shifts right at about 45MPH.