if the explorer already had a v8 you will not need a new tranny or driveshaft unless the engine is more powerful than the transmission can handle (not likely). to answer the question about the engine fitting into the car itself, like i said, if there were a v8 in there before, then no parts necessary, but if it did not have a v8 before, then you will need motor mounts, wiring harness, ecu, tranny, drive shaft, tranny cross member, fuel lines, and air intake. if these are needed just order OEM ones for the explorer 5.0.