The transmission from the 99 Durango is electronically controlled and will have a lock up convertor. Good for a late model swap but not for a non computer controlled car( our cars). The Magnum motors have no provision for a mechanical fuel pump,( Timing cover will need to be changed to an early carbureted LA. As will the cam, ignition,intake manifold, carb, pulleys and brackets from carbed car waterpump is reverse rotation on the 99 Magnum. Will need a 727 trans and convertor. Basically look at the difference between your crate magnum and the 99 Durango. The 99 motor would only be feasable if you can get some kind of ecm harness adapter to be able to use the computer otherwise all the late model stuff including the computer controlled transmission is not going to do you much good. (the trans will not physically fit an E-body any way without some surgery)