Anyone who has been watching Top Gear recently would know how much engines have improved over the last decade. A more modern lump would provlde more power and be more economic to run.
Obiously the older one would have less problems with reliability, which is why older cars have longer warranties and didnt keep breaking down
Difference is that those V8 lumps can pretty much have the pistons slapping around the bore, and they still fire. One of the favs in boat yards with older boats was the old Rover 2.5D. They stink, they are noisy, but they keep on running no matter what you do. On the other hand more modern engines are made with far more precision, but as a result they require far more looking after and maintenance.