Just a note of caution. If you look at 74 Pinto Wagon's stock radiator it has a panel on the left (viewing) side. That panel allows the the smaller 17" radiator to bolt in where a the larger 20" radiator is also available. That would be for '74 and up cars. So, in essence, the '74 and up Pinto's were designed for the larger radiator and the smaller radiator was adapted with the side panel to work.
If you have an early (71-73) Pinto the larger radiator will not be a direct bolt in. They were designed only (as far as I know) for the smaller 17" radiator. This is evident in the picture of my '73, small, 17" radiator (there is no side panel). You must modify the opening to accommodate the larger 20" radiator.