The question is if a legacy engine will run a a DC layout. The answer is NO. But you can run your LC, LC+ and LC+2.0 on AC or DC. Good question!
I also use the 72w Lionel power source. One on each loop of my 17x11 layout. Breaking it up into power blocks is a good idea. And you can use a 54w that came in some of the kits too! I'm expanding my layout a bit and will have one 72w unit and one 54w unit on each loop.
With the intro of LC+2.0 there really is no reason to change to AC. You can get a fine engine with lots of feature for less money. And you save some money also because you wont have to buy the AC transformer.
Jim