Some years ago, Dave Taylor built a beautiful Custodes army, one of my favorite models from that army was a Dreadnaught converted from the Throne of Judgement. I happened to have a Throne of Judgement lying around that I had scavenged parts from, so I decided to use it to build a Grey Knights Venerable Dreadnaught.
To build the sarcophagus, I obtained the bit from the
plastic ven-dread kit from a bitz seller. I wanted the pieces to look
sufficiently grey knight-ish, so I got the helmeted head from the Dread
Knight kit. Lastly, I wanted to build this as a rifle-man dread, after
looking around, I settled on using the reaper autocannon from the
Defiler kit -- Reaper autocannon on a Grey Knights model? HERESY!
To de-chaos the reapers, I removed the bayonets and filed off some of the spikes, then I covered up the Demon mouth with a magazine from the IG Heavy Weapons set.
The arms holding the autocannon were built using the hydraulic cylinders from the IG Vehicle accessory sprue, the searchlight from the same source and some plastic tubing cut at an angle.
And a few paint-in-progress shots: