Here are some shots of the sprues and commentary on magnetizing at the bottom:
https://silo41.co.uk/2014/03/20/chaos-space-marine-helbrute-a-review/ I'm pretty sure you can magnetize the
LC /
MM /
PC, as they're all separate cowling + barrels. You could also use them to convert the
DV MM out if you don't want to use that. It looks like the
ML is its own should mount, and actually all the
ccw options look like they have their own shoulders - I know the scourge does, as I've used that and a right powerfist to convert the
DV monopose

And it looks like there are 4 shoulder pads, with the spiky one split in half.
But yea, you should definitely be able to do a
ML /
LC dread and then swap some arms out on the
DV brute.