Originally posted by Fat Lady
Jonathan Penrose seemed to be equally good at correspondence and OTB chess. He was a correspondence GM and would easily be a GM if he was playing today though I think he only made IM when he played in the sixties.
Hugh Alexander was another strong British player who made the switch and played a few nice correspondence games in the 1960s. In nearer times GM Ulf Andersson has played 30 odd CC games and is 2nd in the ICCF rating list...I saw a couple of his games annotated in Chess Mail and he seemed to play less dryly that he does OTB