I think it's also worth saying that it's equally fair logic to recognize that without the Ace, there would be no Cobra either -
as we know it, that is; though Shelby's dogged determination almost certainly would have led him to forge some sort of a deal between a sports car manufacturer and a US engine supplier.
The progeny of that marriage quite likely would have been a fast and formidable race car. It may even have been called a Cobra too, considering the possibility that a similar day with similar synaptic inputs and stimuli would lead Shelby to have the same eureka dream
(or at least the likelihood that he would've stumbled across the acronym for
COpper
BRAzing at some point).
If such a car did come into existence, though, would it have posessed the striking, almost sexual beauty of that Tojeiro-designed shape that is just as critical a factor in the generation spanning appeal and charisma of the Cobra as it's legendary performance? I say possibly but unlikely.
The Cobra was a perfect storm of unlikely events and characters, all coaxed, cajoled, bluffed, bullied, inspired and led by one driven, remarkable man who pulled it all together and made it all happen. Take away a critical element like the AC Ace, and Shelby may still have built a car - but it would not likely have been the Cobra that we know today. Probably not even close.