After the great tip from FortyNiner, I emailed
http://ucvintagerad.com
They called me back today with a quote of
$89 for a bare core.
8"x8"x2-1/4". You use your old tanks and tubes.
I also found a Chrysler heater core at my parts store that would work. $41 !!!.
7.5"x7.75""x2". Tubes are 5/8", but are short and straight, unlike stock.
Easy to adapt if you're not restoring exactly.
Thanks for all of your suggestions.