Who gives a rat's ass what a Modern Chevy engine can or cannot do? If you are interested, go to the Chevy forum.
When I bought my replica, I wasn't interested in making an exact copy of a sixties icon. I wanted the look of the cobra coupled with an old school ford engine and a modern five speed tranny.
After comparing the FE and the SBF, in regards to weight, power, appearance, cost, size, leaking, etc, I went with a SBF. I wanted around 500 streetable, reliable horsepower, and also wanted to be around 427 cubic inches. Ended up with one of Brent's 438 SBF's and couldn't be happier. No valves to adjust, doesn't leak
oil, and I can actually tell onlookers that it is a 427. And it has way more power than I am capable of using.
But, if originality is your thing, then an FE coupled to a top loader 4 speed is the only option.