well, a 4.9 a cast iron block, very heavy.
a 4.9 will put out 170 hp and 260ft/lbs torque.
a 4.0 puts out 160 hp and 225 ft/lbs torque, weighs a lot less, and uses less gas. some mods can get you to the power of a 4.9 with a little work and a lot less money
if you really want to do a swap, a 5.0 will put out over 200 hp and nearly 300 ft/lbs or torque, weigh less than a 4.9, and go in a lot easier. Unless you are really stuck on doing something different, this would be a much better choice.
if you are looking for more of a challenge, a 4.6 might be a better choice. they put out 310 hp and 335 ft/lbs in the highest performance NA form.
yeah, 4.9s are great engines, but for all the difficulty vs gain of putting one of these engines in, you would be far further ahead going with a different ford engine, or just buying an f150 with a 4.9 already in it