The 440 cast WFNGC will be fine at the velocity the 500 S&W is capable of producing, and in fact is more than is absolutely necessary.
I have shot bison and the similarly sized water buffalo and yak with the 420 WFN (1400 fps) and 400 XTP (also 1400 fps)out of a .475 Linebaugh , the 350 XTP (1350 fps) and 370 WFNGC (1390 fps) out of a .500 WE and a 400 Speer as well as a 405 Remington (1110 fps) out of a 12" .45-70. I've used a 270 spire and a 300FMJ (1950 fps) out of a 12 1/2" .375JDJ, but that's another kettle of fish.
I've used a .416 Rem. Mag. and 400 gr. Hornady soft points (2270 fps) on cape buffalo, which are generally smaller than bull bison.
All these critters fell over dead in fairly short order. The quickest as well as the longest death both came from the .475L, which simply points out that there are no absolutes.
One of the things you should consider is the fact that bison are herd animals, and you must be absolutely certain of what's behind the animal you want to shoot. With herd animals there is definitely a case that can be made to avoid a bullet that will over penetrate. I like the XTP's for that very reason, but once again, the bullets you suggest will be fine, with care and prudence.