Heater Core NON-AC

[NavyChief]

Hey all! Since the defrost in my truck was not working I decided to rip out my heater core a replace it. Well long story short 2 dead mice and a nest later the heater box and all the components were cleaned out! Unfortunately I have hit a snag. The replacement heater core is the newer aluminum and is a tad bigger than the original clamps that held the last one in place. Does anyone know where I can get a replacement copper/brass heater core or am I stuck with fabricating some brackets? I did put the aluminum one in but I do not like the idea of it just sitting in the housing and not clamped down.

Thanks!