Completed this trip on boxing day and had a great time! We started off at marathon road and took a little loop about a third of the way up on a track that linked into Williams road (Valencia creek track) and then back onto marathon further up. Once we were back on marathon, we drove up to Castle Hill and then onto the Pinnacles. We we're lucky and had a fairly clear day which meant there was a good view at the Pinnacles. From there, we ended up heading down Billy Goats Bluff track which was a lot of fun and then along the crooked river through to Dargo.
I would recommend a good set of All Terrain tyres at the least and a vehicle with some good clearance as parts on Billy Goats can get pretty rocky with a few little drops throughout.