2004 Honda Civic Ve Read This Somewhere That You Cannot Install Older Engine On

I've read this somewhere that you cannot install an older engine on a newer vehicle, unless that older engine had the EXACT SAME emissions equipment down to EXACT same part numbers as the new vehicle (as in, they re-used the same old style emissions equipment on the brand new vehicle from the factory). So, would you know by chance if the 04 Civic and the 95 civic have the exact same emission equipment? This being my first car I'm so lost and not so knowledgeable as far as cars and engine is at concern.