There are 2 common designs for radiators. These are named for the direction of the coolant flow, also can be distinguished by the position of the tanks. The first one is called a down flow. In this design the coolant flows down from top to bottom tank. The second is called a cross flow. In this design the coolant flows horizontally from tank to tank.
Before measuring a radiator always make sure it is in the upright position. You measure only the core (just between the tanks and side pieces) which is the central part of the radiator. This contains parallel rows of tubes and fins. Remember to measure only the core to determine the size of the radiator.
This is the distance between the top of the bottom header and bottom of the top header.
This is the distance inside the 2 side channels.
Carefully insert a piece of wire through the core until the end is flush with other side. Mark other end of wire (where it is flush with core), carefully take out the wire and measure to get the depth.
A= Core Height, B= Core Width, C= Core Depth, D= Header Width, E= Header Length, F= Overhang FRONT=Grill side, REAR= Engine side