The DT408 is almost the same engine as the DT466. As memory serves me, the main difference is the cylinder liners and pistons. They are no longer available as IH reman engines; you'll get a DT466 in it's place. All the external parts should interchange. When it's time for a rebuild, you can build it into a DT466 quite easily (In fact, I don't even know if the 408 pistons and liners are even available).
Good engine, just as good as the DT466 (since it uses the same block and just about everything else).