How many books hours does it take to replace motor 2001 Chevy blazer 4.3 L 4 x 4
Alldata says about 12.5 hours for a simple swap, and as much as 21.5 with transfer of components (aka "long block") and accounting for AC and a skid plate, if present.
Those numbers are for experts very familiar with the job, and does not include the various rusted and stuck "gotchas" that kyle_engineer hints at.
Believe me, they are there in force and plentiful. Labor manuals are for setting baselines, usually in a dealership flat-rate environment. Your mileage will Shirley vary...