When got my 67 Barracuda it had a later slant six radiator. It worked OK even when I put the 340 with the 70 up water pump in it. Unlike a correct pre 70 v-8 radiator, it was possible to find both upper and lower radiator hoses without resorting to flex hoses (never good for flow). However especially with A/C, in the summer stopped in traffic, thats when fan shroud and sufficient core will become important.
Another story from yore.
At some point I lucked into finding a factory flex fan at a junkyard.
Leaving the parking lot at Chancelerville (CW Battle) luck ran out. Half a blade seperated from the rest and fortunately the side of the battery tray took the majority of the hit. Limped into Fredricksburg with some directions to a parts store. Replaced the battery, the waterpump, the fan and used up my supply of baking powder that was my backpack for emergencies. Fortunately did not hole radiator. However my salvage yard fan shroud was out of action for the rest of the trip.
So much for factory parts. LOL. There was probably just a little crack that had started where the flexible blade was riveted to the stiff center.
PS Those bubble top radiators are somewhat scarce so if you ever don't need, find it a good home. They fit nicely in the pre 70 cars.