['ol Pinion head]

Lot of options.
-personally, im not one for contrapting together some sort of "adapters".
-if the radiator is a 4 core, & otherwise in great shape, & the spacing between the two AT cooler lines is 8 1/2", I'd have the pass tank replaced w a good used one. They are out there. From the limited view of the pic , the radiator is an aftermarket replacement, & that particular style of aftermarket tank is not that hard to find. Having stripped a ton of crossflow radiators for serious restoration/original Harrison tanks & rails, the aftermarket style tanks were often chunked or left to pile up then I gave them to local radiator shop owner that recores my rads.
-if its an aftermarket 3 core, I'd prob pull it, & replace it w either a replacement alum radiator, or if a stumbled onto a deal on nice used 4 core Desert Cooler or a General Radiator.