Starting install of BellTech 921SP lowering kit tomorrow night on my 2003 F150 Harley Davidson. I couldn't find a good Thread so I will be posting pics and knowledge gained.
my only concern in regards to ride would be those belltech shocks. like i said before, pick up some lightning spec bilsteins and some shock extenders for the rear
I started with Rear. As said, the worst. Best method I found was cutting off rivet heads with air chisel. Get between frame and hanger with chisel at easy to get to rivets. Once you get one to pop the others get easier. Cut the remaining rivet off with chisel. Then change to round tip and hit remaining rivet until pops thru. Two toward front of truck with have one layer of frame and go pretty easy. The two toward the rear will have 2 layers of frame and take 3-4 times effort.
Then just clean up & install new bracket. (Note: bolt holes will not line up but are Grade 8. Just get all started even at angles and tighten up)
Leaf springs are a lot easier. I used original U-bolts. Still plenty of threads left after shim installed. Also didn't see a reason to cut center bolt.