Hello, I rebuild and restore them here at my shop. I also have several original boxes that are good for cores and more boxes for parts. I can build you a box using one of my cores and sell it to you outright, ready to install. I have the original heater cores rebuilt (the aftermarket heater cores do NOT fit that great). I also have the evap cores pressure tested and cleaned. Let me know if you are interested. I can get one ready pretty quickly. I think you will find that Classic is multiple months behind on any shop work as they are running a very limited operation with the Covid mess going on. This is what they told me when I ordered some parts from them last month.
Thanks, Steve