Chaos in the Underhives

I am currently working on another Warhammer 40K / B/X D&D mashup. I am converting the B2 Keep on the Borderlands to use and hope to playtest soon. The game will be a dungeon crawl / adventure game about rooting out Chaos infected elements in the name of the Emperor (much like Dark Heresy only using B/X D&D).

Available character classes will be:
Inquisitor (Cleric)
Psyker (Magic-User)
Marine (Fighter)

Some possible character classes (still undecided)
Eldar Farseer (D&D Elf)
Squat (Dwarf)
Assassin (Thief)

This is very much a work in progress, but I am concentrating on the Caves of Chaos first so I have something to play-test once it is ready. Basically the Keep on the Borderlands is the Hive City of Volgograd IV and the Underhives of Chaos are where the main adventure will take place.

I have already begun work on the conversion and here is my sample "start" text from B2:

Start: The passageways you have been marching through have been getting more dense with debris, and gloomier than before. The thick, twisted steel beams and exposed wiring snagging on equipment and tripping your steps as you force your way deeper into the underhives, seems to warn you about the way ahead. Relentless, you pass deeper into the bowels of the city, and suddenly the way ahead is clear and you stand in a city square that looks like a canyon. The walls rise hundreds of feet above you and before you are three walls with various balconies with looming black openings into the heart of this secret part of the city.  The air is thick with the smell of burnt rubbish and the ever present smell of machine oil.  Rusted and abandoned grav-bikes litter the ground before you, picked clean of parts long ago.  Graffiti covers much of the walls, tagged by many of the gangs and cults of the hive city of Volgograd IV.

You know that you have certainly discovered the Underhives of Chaos.