Ops Limits
The operating limitations specific to your aircraft trump any opinions. Read them and do as they say. There have been many changes over the years. But just about all of them have required working with the FSDO for a major change, which of course you have done with the engine swapout.
Besides throughly testing the engine, you really need to flight test the aircraft, gathering the new data such as Vx, Vy, Vso. Most likely this engine will have an impact upon flight characteristics and W&B that were different than the first. As Mel stated, 5 should be the minimum, but I suspect it could, and should, be longer.
Be safe.
Vic