Question on SFBD

This might be a crazy question for some of u guys but ive been looking at some guys pics of sfbd builds. My question is when building a frame on a jig are u still dropping the frame horns for your bd or are u getting your drop out of your new body mounts? If anyone can explain that to me ill have it all together thanks guys

Your replacing a factory frame rail which is anywhere from 6" or taller with a 3" tall piece of tubing. So when you lay your cab on the new rails its 3 plus inches lower. you want your frame horns to stay the same, but you will have to Z the front radiator support. Just get the frame layed out flat on the frame stand, and weld the front clip in place to the frame stand, and then cut off the factory frame rails before the fire wall. Then the fun begins. I hope I was some help