Maybe you can push the two parts of the mustang split to the sides a bit to create a bit more space between the A and D string.
The Musicmaster just used a six polepieced Strat pick up. If you buy a Duesenberg you get a six pole humbucker too.. I know lots of guys experimented with other Strat pick ups (humbuckers, stacked humbuckers, hot, vintage, ...) in Musicmasters. So I don't think that pick up is that good.
I think the sound of those basses also have to do with small and light bodies and relatively short necks. Maybe even more than the pick ups.
So my conclusion:
Musicmaster pick up: Not that good.
Mustang pick up: Good, but also because the rest of the bass, so maybe not better than a vintage P pick up.