There was already a thread on Marciano-Williams which produced a lot of heat on the forum not seen in a good while, but I will go with Marciano both times. Ruddock is totally gone no later than seven, and gets absolutely pounded. Williams probably doesn't last much longer, but gives a much better account of himself.
Marciano's manage Al Vile (Rocky's wording) supposedly resisted a title fight with Nino Valdes fearing the big Cuban. Williams, Ruddock and Mac Foster are a similar size and heavy fisted. The answer is I don't know ?? as Marciano didn't fight anyone that big after Carmine Vingo and he wasnt at that level anyhoo.