The gen 1 Lightning is a huge departure from 92-96 F-150 and even further from a 91 because the front clip is different. The following items are Lightning specific:

Engine
Trans
Rear end
Springs
Shocks
Sway bars
Frame
Seats
Wheels
Front valance and grill

Every thing can pretty easily be changed other than the frame. To be honest, by the time you buy and install all the Lightning parts you could have bought better stuff from the aftermarket and had a better handling and faster truck for less money. The L1 OE parts are getting pretty pricey.