i have a 96 f150 with the 300l6, i have also added a msd 6a box, ford motorsport 9mm wires(v8 set made to fit) copper dist cap and rotor, and a msd blaster coil. i also added an open element k&n air filter. i did the mods one at a time, other then the msd box and coil, did them at the same time. i felt a good bit of difference with each mod. only mod i wish i have done first is a electric cooling fan,which i still need to do, also my trk is 300l6,e4od and 3.08 gears with 275/60r17 tires on lightning rims. i haul my race bikes in and out of state a lot while hauling a pop-up camper and i do believe each mod was worth the money. also use only ford/motorcraft factory style spark plugs.
just for a FYI, msd stands for multiple spark delivery, they offer 3 fires with each cylinder cycle instead of one. which will help any engine run more efficient. i can get into how it really works but my post is long enough as is.
forgot to mention, i also have a 3" free flowing exhaust system.