Radiator ID help needed

Hi Guys, been a while since I checked in, but I'm thinking of a replacement radiator ahead of my 340. The one I'm running I do remember pulling from a salvage yard Dart, and I believe the numbers say it was from a 1972 340 car. (Core 22"w x 17"h and total radiator height 22". Inlet and outlet on drivers side.). Numbers on the tank are 18398 and 3574 658.

My confusion is that these side flanges come to the rear and bolt holes are even with the back side of the radiator. All the replacements I have seen so far seem to have the flanges mounted so bolt holes are flush with the front of the radiator, not the rear. (Admittedly in my case, my radiator support set up is all home made so my existing works fine.) What am I missing here? Why does my stock radiator seem to be different from all the replacements?

Did I at one time have the side flanges mounted backwards??? I certainly have no memory of doing this, but I guess it's possible. Were there any A-body radiators with the mounting flanges flush with the rear of the unit??