Glider with a different engine

[Mrkentee]

Looking at possibly buying a friends truck. It’s a 2014 Fitzgerald glider which came with a 12.7 litre Detroit. In 2018 he bought a brand new series 60-14 litre from Detroit and had it installed.
My question is will that engine having a 2018 serial number ever be a problem as far as emissions go? He says he just claims it’s a 12.7 pre emissions model if asked.