In 73 the factory placed a 26 inch radiator with shroud, coolant resivoir, and a charcoal vapor canister against the inside of the core support. All they needed to do was widen the opening, move the 4 welded nuts and relocate the horn(s) under the battery tray.
The only other difference between my 73 and my 67 is the 73 has the lower hose on the right side. A diiferent water pump accomodates that but hides the timing scale.
This is all about stock radiators though. I dont know about aftermarket.