That would be some match up prime for prime wouldn't it! John was great but I don't think his style was made to get past Foster's long arms and Bob knew how to put full power at the end of his punches. One knock on Conteh by some was his inability to duck or easily bend down and that was because of his weight on the back foot style, lacking that in defense and not being a fast mover makes me think big Bob would have caught him over 15.
Brits tend to rate him just below God for some reason. Good win over Yaqui Lopez, but it was certainly hard-fought (as were many of Yaqui's losses). Other than that, who did he ever beat? Ahumada? Not exactly an ATG, and Conteh lost to a very pedestrian Euro talent Mate Parlov. Got a gift draw against Jesse Burnett when knocked down twice. I think his chin was below world class. Certainly a slick boxer and very charismatic and fun to watch. If you want to create a fantasy world where he didn't have brittle hands and he was the most dedicated and focused warrior who ever lived, OK, go ahead. But let's do that with all his opponents (real and fantasy) and take away their weaknesses, too. Rating what he actually was rather than what someone wishes to imagine he might have been, it's ludicrous to put him in the same class as, say, Michael Spinks. And he surely fell short against Saad (twice). In the latter half of the 1970s/early 80s, when the light heavyweight division might have been as good and as deep as it has ever been or will ever be, he isn't among the tops like spinks, Saad, Qawi, Eddie Mustafa, etc., and I rate him below Galindez and Marvin Johnson as well.