Heater core re-cored? Or such thing as a universal one?

Rock Auto shows to have 2 different ones for 78 cordoba non a/c ,1 is $47.79 the other is 67.79,,, the A/c shows out of stock. The photos you show , the tri-angle shape takes a blower which mounts from outside straight to heater box which has 4 studs, the other round hole takes a different blower motor that the heater box under dash is mounted , with front removed, you mount motor and bolt it inside ,then put heater box front on.