are you going to necessarily trust that? I mean, all these years later? eg. I remember a thread here where someone linked to an article online where some dude said he was the guy who did (at least some of?) the whistling for the score of Leone's movies; whereas I believe that according to Frayling, Alessandro Alessandroni did the whistling. This is the sort of stuff that, four and a half decades later, we may never know for sure...
I was happy to accept Volonte's English voice as Frees for a time. Upon reflection though, they really don't sound much alike. I don't know Bernard Grant but he seems a more likely candidate.