My rule of thumb for radiator size. The radiator surface area should at least the same as your engine's cubic inches, 350. I try to get the biggest radiator I can fit.
I swapped in a Chevy 350 into my Dodge D-50 4x4 and I run a 27x19 inch 2 core Griffen aluminum radiator. The radiator barley fits. I added a 1/2 inch spacer between the hood hinges and hood to hold the rear of the hood about 1/2 higher allowing the hot air to escape. I have a light weight plastic fan driven by the engine and two 10" electric fans in front of the radiator. I've never had to turn the electric fans due to overheating. It runs about 190 even when I am crawling.