I think the majority of all e-bodies were 318 2bbl and 383 2bbl, so my response would be to choose one of those. But I guess part of it is understanding why the original car was built. I don't get the impression that it was meant to be a "wow factor" factor, with big crowds around it at international auto shows. It sounds like (and correct me if I'm wrong) that it was more of a proof of concept to show what was needed to make the car a practical reality. If that's the case, I'd stress the practical reality part, and definitely go 318 or 383. If it was meant for the car show circuit, then 340 or 440.