With glue and clippers!
I've just built an old FW pred with lascannons and lascannons, because I want my world eaters to have something that can take out armour, and that seemed the best load out to take.
The 3 new plastic ones I've earmarked for the Iron IV, will have autocannon turret and lascannon sponsons, for nostalgia and cheapness, and means they can have a pop at most targets