Rebuilding heater box, replace core?

I ALWAYS prefer copper over aluminum for radiators, heater cores etc. Especially if the aluminum is capped by plastic tanks.
When I redid the heater box for my D150 (put factory ac plenum in place of factory non ac system) I couldn't find copper, American or Canada made replacement / so since I had 3 80s D/W truck factory ac boxes on hand and only need 1 good heater box right now, (if my son does anything with the 83 he has it'll be 2 out of the 3 that I had)
I went thru the 3 and flushed them all out with sno-bol then plenty of water/ and tested them, and picked the best of them plus a seal kit from DMT to rebuild my heater box.
Like has been said above once I go thru all the work I have going on with this truck it won't be driven much in the cold months anyway. I might add some shut offs at the firewall just in case, for insurance in case I do get a pinhole.
I have had many instances of good, used factory original parts lately (besides HVAC parts) being a better choice than new Chinesium.