looking to purchase a 72 to 74 cuda, is a 360 engine that much
 

different than a 340?

I don't understand your question. Are you talking about buying a car and swapping in a 360, or buying one with a 360 already there, or what?

360's are great engines. So far as swapping, they are a bolt in except for a couple of minor things. The oil pans on 360's are different than the smaller LA engines and they are externally balanced, so they need the flywheel/ converter, and front balancer that belongs on the 360.