Just spoke to a friend who I know through the store, and he said that he had a Leviathan Dreadnought with a Grav Flux Bombard and Siege Drill he'd be willing to sell me for $30. Apparently the legitimacy of it is questionable, but it's unassembled so I asked him to bring it in tomorrow and I'll have a look at it. For all I know, it could be perfectly fine just discoloured, and I can build/paint it how I wanted to originally.
For context, a Leviathan Dreadnought looks like this:
The plan is to build the main body of the vehicle with Twin Volkite Calivers (shown in the above picture around the waist), and then pin the arms where they adjoin to the shoulders so as to allow them to be swapped around. Then they'll be painted as an Imperial Fist to serve as part of the Primarch's Chosen alongside Terminators and other Dreadnoughts.
