That notch on the dist hold down is there so you can't adjust the magnum dist but so far. Look at the housing on the magnum dist, you'll see the recess that the tab fits in. Absolutely no problem grinding it off for your purpose.
S..........what I figgured, LOL. I didn't feel like hosing up another LA one so I just ground it. That clamp will have a mag dist under it, of course, when that engine goes into the Dakota. I may find another Mag clamp..........I've got at least 6 or 7 LOL