Bill,
Yes, the lowering shackles from DJM Suspension will work to drop the rear of your Ford F150 Lightning.  Ford already lowers the F-150 Lightning by two inches in the rear with a de-arched leaf spring.  The shackles from the standard F150 to the Lightning edition are the same.

Go ahead and use DJM Lowering Shackles (Item # SH10142).  They will raise the rear mounting point of your factory leaf springs by 4 inches, which will lower the rear of your truck by two inches.  This is an easy and common installation.

This would also be a good time to replace your rear shocks.  If they are old or have a lot of miles on them, the added stress of being squished an additional two inches all of the time (because of the lowering shackle) could be enough to make them fail.  DJM sells a full range of lowering shocks that are physically shorter and provide for superior ride quality on lowered trucks and SUVs.  The correct rear lowering shocks for your application are item # 2200DJM.