If you look at the nose on the ebay 2451's ( they are real ) you will see that 4 additional holes were drilled into the 2450 snout ( that also had their magnet cover flanges cut off ) to allow custom LONG bolts to hold the snout to the magnet. It's a whole lot safer to redrill the aluminum snout than drill/tap the super strong magnet. I did it to a pair and it was an exercise in chip management....
The 2450 and 2451 use the same magnet BUT the horn mounting holes on the 2451 are standard whereas the mounting holes on the 2450 magnet are for the snout ONLY and are much wider spaced.
Back when I had many of these variants in the shop I photographed the differences and if I find the pix I will post.