Playing in the local Crusade of Fire campaign has given me an opportunity to get back to work on my Fire Hawks army. Besides getting some more of my stuff assembled and painted, I've had a chance to put my first Blood Talon Furioso together.
I clipped off the "nubs" from the arms, drilled a hole and flush-mounted a magnet. I also glued a magnet into each of the fists, the bottom of the torso and inside each front armor plate. (I did put the Librarian-specific top bit on the center of the front plate instead of on the main body of the dread, so I didn't have to have it on all versions.) Once that is done, changing over to a different version is just a matter of changing out an arm, fist and the front plate.
The great thing about the newer dreadnought kits (like this one and the Space Marine Venerable Dreadnought) are that the new arms are interchangeable. There's quite a variety of dreadnought arms out there to make some really characterful kit-bashes.
I think when I magnetize my next Blood Angel dreadnought I'm going to put the magnet inside the fist, behind the outer layer. I'll still clip off the nub, but the force for the two magnets right next to each other is pretty great, and the hands are pretty light pieces. I've got at least one more to build, so look for that one soon.