Summit Racing has a 24x16x1.75 aluminum radiator for $152.95. (PN
SUM-380645) that has small end tanks. The core area is 15x20.5.  A
little more than half the area that Paul recommends.
I hope to flow check my valve in the next day or two, if I can get an
extra set of hands to help.  Karibian

15" x 20.5" by 1.75" thick that is 538 cubic inches. Only a little
on the small side volume wise. It will be highly dependent on the design of
the in and out ducting. Well ducted it might work fine for a non p-port engine.