Honestly, I wouldn't worry too much about the extra 100lbs or so especially during a wreck.
That stuff is going to be scattered and littered all over the highway during a wreck. No one is going to recover it all to weigh everything collectively to find out you exceeded the door stamp by 100lbs.
Does anyone have the part numbers for these rear leaf springs? In case someone wants to retrofit their non HDPP F150 with the leaf spring packs with a higher spring rate. I know this won't increase your actual tow or payload rating legally, however, it should improve handling when the rear...