These are built using 2 Mastercrafted models hulls, designed by Tomcra, who also designed my Abrogator kits. I've had them for a few years, and was holding off building them until my chassis kit was done. Since that's never likely to surface now, I decided to crack on using Chimera bits. The Mastercrafted kit comes with 3 variant gun barrels, and it was one of these I used (after some sawing) to make my Conqueror.
I still need to source another Chimera turret hatch to finish the second Thunderer, as well as add some grabs and Khornate symbols.