Danielbolt,
A check of the earlier 1929-41 parts book
https://chevy.oldcarmanualproject.com/parts/1929_41/41cp026.html shows the 1939 JC model radiator # 3112130 to be the same between the 2 books.
But the earlier book shows # 3113453 for the 1940 KC model radiator (looks like the later book shows a newer # 3117627).
Crazily, a quick web search for GM# 3113453 shows this
radiator offered.
Not sure if you can take advantage of the offered item (not mine btw), but if nothing else you could capture screens shots of the pictures to use to help identify an original radiator.
NOTE: If you can't manage to snag that item, let me know so I can post that ad in the
Other Online Sources forum so maybe another Bolter can snag it.
