FOUR LINK AND NOTCH POSTION

I AM TRYING TO FIGURE OUT HOW LONG I WILL NEED MY FOUR LINK BARS. THE TRUCK HAS THE STOCK LEAFS AND 4" LOWERING BLOCKS RIGHT NOW. IF I PUT A TAPE MEASURE FROM WHERE I PLAN TO MOUNT THE BOTTOM FOUR LINK BAR TO THE CENTER OF THE AXLE IT MEASURES 37 INCHES. BUT IF I MEASURE THE 37 INCHES FROM THE SAME PLACE BUT HOLD THE TAPE UP IN THE NOTCH WHERE THE AXLE WILL BE WHEN IT IS LAYED OUT THE 37 INCHES IS WAY TOO SHORT. IF I MAKE THE FOUR LINK BARS LONGER TO FIT IN THE NOTCH BETTER THEN WHEN I LIFT IT IT WILL PULL ON THE DRIVESHAFT. DO YOU JUST GO WITH A MEASUREMENT IN THE MIDDLE?