If it were me and it came down to the motor, all other criteria being essentially met (differences considered splitting hairs), I would opt for the SO. I think the cammer is at the panicle of ford motor building, there is no better motor in the "period correct" era, and few can compete with it today. There's a guy out there who can afford anything, and he has one of the best "authentic" car collections money can buy, he has one of the best "authentic" motorcycle collections out there. He doesn't have an original cobra, but he did have one hammered out from aluminum stock like the original - this before Kirkham and others were available. His had an FE in it, being a man who could afford anything, and also a man who wanted to be period correct, he swapped the FE out for an SO.
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