B Body rear end housing

I haven't ran one but I've read about guys that do run them. As long as you move the perches and run tire/rim combo that keeps the wheels/tires inside the fenders your ok. I'm not quite clear on your question about the perches but I assume your referring to the yoke being angled down 5 degrees? If that's what your saying that's correct. They need to be angled down like that because when you accelerate the rearend naturally want's to twist upwards at the pinion so the introduced angle cancels out under motion.