Story reminds me of the pristine 302 powered '77 Pinto wagon father/son project we put together for his High School ride back in the early 80's. Beautifully executed installation. Appeared 'factory' or better -if I do say so myself.
Before son headed off to collage he sold it off to a local ...or perhaps I should say a loco. Guy stops by a few months latter, big hole hacked through the hood to clear a gigantic steaming truck radiator sticking up about a foot above the hood, installed he said 'to cure the 'overheating' problem. And it was still overheating.
Huh? What overheating problem???
Turned out the 302 had developed a head gasket leak that was allowing the escaping combustion gasses to over-pressurize the cooling system.
A 50 gallon radiator would not have fixed that cooling problem.