Bob Foster heavyweight champion?

then why did he never translate this ability into a win over a world class heavyweight?

 

He definately looked out of his depth at heavyweight, one of the great light heavies though, stunning ko power.

 

the fighters who beat him were head and shoulders above fitz and corbett.
ali and frazier for instance

 

Even the light-heavies Foster beat weren't much good.

 

I'd pick Braddock to comfortably beat a heavyweight version of Bob Foster. I don't think I'd favour him over any of those you mentioned.

 

But he wasn't just loosing to the Ali's and Fraziers of the world.

He was also loosing to the second and third teir of heavyweight contenders.

Whatever you think of Fosters era is irrelevant because he achieved nothing at heavyweight at world level in it.