I have the standard heater in my 49. The core is made circular and in two pieces with a hole in the center like a donut. The fan motor mounts in the center of the hole. The two tubes go thru the firewall from the inside and there are 3 mounting bolt holes in the firewall if it is a standard. There is also a flat plate about 4" in diameter on the firewall in that location. I think that it has to do with the deluxe heater. These heaters occasionally show up on eBay but you should be able to find one elsewhere. If you need more help you can email me.
Bill


1949 Chevy 1/2-Ton
"Sedgewick"
In the Gallery
1989 Caprice