It is not unusual for a Repair Garage to obtain take out engines from Auto Recyclers. They may be local to you or actually quite some distance away. Generally the supplier guarantees the engine to the garage to be in good running condition, they are usually started and run for a short time on a pallet before they are shipped. The supplier attempts to verify
oil pressure and no unusual noises but when doing so do not generally have any mufflers. They play the percentages, as does the garage. If there is an issue the supplier will replace the engine but there wont be any re-imbersment for labor to pull it out again so you may get resistance from the garage, because it's on their dime. Stand your ground. The suppliers generally provide mileage info with the bill of sale to the garage.