How long to replace engine?

"Book time" referencing one guide shows just swapping the engine without swapping any related components (including wiring, intake, etc) at 15.7 hours. Add 3 hours to replace a "complete assembly" with swapping parts. Add another 5 hours to replace the assembly as a "long block" -- 23.7. Actual time? It's completely relative to the technician and skills as well as the shop environment and equipment present to do the work.