$200 to $2,000+
Long block that you have not seen run but looks complete and a motivated seller, $200. I paid that for a already removed on the ground 5.0 with intake and a butchered harness and no front dress.
Good running engine with some speed parts, the price can go way up.
How complete is the engine? Just an engine, not enough for the injection to work I wouldn't pay over $500 unless they can show some real good reason for it (dealer put in a factory engine 2,000 miles ago, etc.)
Complete with all the little stuff to get the injection running, (computer, harness, all the little solenoids that you may or may not use) air filter housing to cats and everything the belt spins over, about $1,200 tops.