Speaking only for the Vengeance class series, all the Chaos and Imperial Weapon batteries, lances, and launch bays from the plastic cruiser kits fit ok. Thats how I built my Exorcist class. I think GW used to sell an Avenger when the model first came out, but it was discontinued as the Vengeance could be made into all the relevant types. I seem to remember (it was a few years ago) that it needed a tiny amount of filing to fit the weapon slots on snugly, but otherwise, no problems.
