Drop: 5/7 kit from any reputable company. I have used Western, Belltech, DJM, heck I have used AIM... That is what drop is on that white truck. If you go much lower than that, bag it...
Engine: I HIGHLY suggest getting an LS motor based on you current stable.
Bumpers: just get the painted bumpers and paint them body color
B-pillars - You are never going to find them in the color of your interior. Even GM dyed them to match. Not sure why everyone wants to fine them already dyed, but I would get them out of a junkyard. I got the whole interior out of one for $50 before.
Bed sides: If you can patch it I would. I sell panels for the trucks in the store (big banner at the top of the forum)