It's most likely a Switched Mode Power Supply (SMPS). I'm not saying it couldnt be a linear regulator without seeing it,but at that power level 720W its likely an SMPS.
You might want to try something less ambtious if this is your first foray into SMPS's . They can be difficult at 7W let alone 700W.
A good basic IC to use; to learn some basics about variable linear regulators is the old LM723. You will soon see the problems and expense of building a linear regulator at 12V/60A.
A good basic SMPS CONTROLLER to use is the NCP3063 which is an upgraded version of the old MC34063A-D.
Googling anyone of those part numbers will get you a wealth of info.
Everything you could want to know about SMPS well almost; nothing beats frying a few controllers and what not on the bench;-)
Small steps first grasshopper;-)