This conversion uses parts from the Immortal kit and the Warriors, I made my Immortals using the instructions and armed them with Tesla Carbines, but this left oodles of spares and the Deathmark rear torso's and Gauss Blasters as juicy leftovers... so using the legs, front torso and head from the Warrior and the rear Deathmark torso, arm and weapon from the Immortal leftovers, I constructed a fairly convincing new squad of Immortals.
I am yet to fill the joins with liquid green stuff, but both share the larger shoulder blades and bulked up profile over the thinner warrior's frame. The only thing missing is the distinctive wire leading to the gun - I may later construct some using guitar wire, but for now it will be left off. The Gauss Flayer is not plugged in, so neither are my Gauss Blasters.
Hope this gives you some ideas to use up the spare kits you may have laying around.