Period racers built with GM engines are fine, like the Cadillac Allards, but I do decry the builders of today (on both sides of the Atlantic) whose instinctive reaction is to “put a Chevy in it…and call it good”. Shows a real lack of imagination and a serious appreciation of history.

It’s not like Ford V-8s are hard to find, terribly exotic, or too costly for Cobra replicas.

I hear what you’re saying, but one could simply say, well, it’s just a look alike.
I guess it would depend on how accurate one was trying to be.
Can’t say I’d want a Chev motor in an ally bodied, authentic repro chassised Cobra, but a plastic kit car? What does it matter? It only has to make the right noises. 🙂