If it was a straight swap with every thing in place on both engines, like having the 2 same vehicles side by side, and had the same equipment, then one was on the ground. Pulling one out and the other went straight in there with no modifications, the guide says 7-8 hours.
In the real world it takes ever how long it takes!! BUNCH of different scenarios possible with an engine swap! There are time GUIDES but that is all they are,,guides! Rarely do things go as planned or expected!