The Stovebolt Site Forums The Shop Area Interiors fresh air heater pre 53 vs 53/54

The deluxe fresh air heaters from 47 thru 52 appear to me to be different from the 53/54 heaters, in that the nipples on the core are straight across from each other on the early heaters, and have a funny little offset on the 53/54 version. I think that they look identical other than that. Am I right? So, my 53 core leaks. If I can't get it repaired, and I come up with the earlier version, it appears to me that the only issue to installing it in my truck would be blocking one of the holes in the firewall and making a new one to line up with the nipples. Am I right about that??

First while the heaters are different, I see a very slight difference in the core inlet/outlets. It would not seem to be enough to matter?
Early heater back side. It may involve a little roto-file work if they won’t move enough by hand.
https://www.flickr.com/photos/advance-design_parts_co/46033227702/in/album-72157631868452754/
1953-55 version.
https://www.flickr.com/photos/advance-design_parts_co/50865146521/in/album-72157631868452754/

The cores are indeed difference both in the inlet and outlet placement and also the physical dimensions. I went through the same thing trying to find a heater core for my 54 style with the side door. Someone makes both cores but I don't recall who. even mounting is different. One has three screws and the other four.

i saw that classic industries has new cores for sale but man they do seem a little pricey