If your truck is equipped with a SOHC from the factory the 5.0L conversion is basically a bolt in affair, but it does require the entire V8 drivetrain, not just the engine.
The 5.0L and the SOHC 4.0L make similar power to the wheels in stock form, but the 5.0L can be upgraded WAY beyond the SOHC potential.....the 5.0L aftermarket is huge