I put a MSD ready-to-run distributor on my 400 this summer. I really like it. Easy installation and I think the car runs better that it did with the old points even though the points were in good shape. It definitely starts better. I have no experience with the Mallory, so I can't give you a comparison. However, I have heard good things about them.
One thing about the MSD that I have heard is that corrosion can sometimes be a problem with them. I haven't run into this yet, but it's something to watch out for.
