Use your old fuel injectors, sensors, intake. No "computer crap" from the replacement engine. Just use the long block (engine block and heads) from the replacement engine. Oil pan and valve covers, maybe.
Buying one of these engines w/out hearing it run is very risky. They're all ticking time-bombs. I'd would consider a used engine w/out first replacing all the timing chain related components. For what it's worth, the bottom ends on the 4.0L's are very reliable.