Blown engine

Not necessarily, but it makes the swap go much easier. An engine from a different year could be missing a port for a sensor, or it could have too many ports, some of which must be capped. For the next model year, the manufacturer could shift the location slightly for an engine mount to correct a vibration complaint, make room for a new part that was not used last year, or to introduce the first of many design changes. GM is well-known to have a lot of variations of parts that often don't interchange. I would not feel confident until I spoke with someone who already went through this or who knows there will be no issues.

Sometimes you can get an idea too by asking at the dealer's parts department. They will have a listing of engines available, and those are usually listed by the years and models that one part number fits. If you find one engine listed for your truck and the donor truck, that is a good sign there won't be an interchange problem.