It’s possible the serial tag was moved over but I don’t believe it common to do it but maybe a more thorough marine company did it vs what I recall hearing/seeing in years past from others.
That location is unique for Mercruiser and generally a remanufactured engine from MerCruiser would also come with a different tag number that usually started with a 9******* would be mounted there but using that new number doesn’t help much at finding parts like I posted above but not impossible either.
If the block came from anyone else then I believe that area come blank and maybe someone put the tag back.
At first thought I’d probably just assume the engine was still original had I’d seen that tag unless you mentioned a new engine was changed then I’d be trying to look real close at the tag to see if there’s any indication of the tag being removed and replaced via bent/damaged, etc..
Maybe
@Yegboats might happen to see something in the history of your number.