R12 vs 134a

To answer your question, yes pretty much EVERYTHING is engineered/designed differently between the two systems. I went to many tech seminars when the change over actually happened. I distinctly remember them emphasising how the condensers were quite different in the ways you indicate. Now, having said that, I have almost never changed them during a retrofit. The slight loss in performance never compared to the cost of replacement. Same with the hoses, heard all the horror stories about how 134a was going to escape through them very quickly. Never really happened. To me the most important thing was just getting correct capacity. Usually around 85%. BTW, Chrysler's were always the worst performers of retrofits, but I'm mainly talking about late 70's-.80's vehicles. If we were doing a retrofit and the original condenser was bad, we would always buy a 134a compatible unit.