How many hrs does it take to rebuild a 5.7 hemi

That's like asking how long does it take to repave a road. It depends on the engine's condition, and whether it's being done by trained mechanics or monkeys in a zoo. Hemis take longer than most other engines; that's about as specific as I can get to such a random question.

If the shop is good and has all the equipment your looking at a week if they don’t find anything wrong with the block or heads and can do a basic rebuild. Any other stuff like balancing or head mods will take more time.