Man vs boy and that's no slight on Hill. Foster would jab him into submission with the threat of the huge left hook and right hand ever a threat. If he couldn't get past the Hearns jab with the threat of the right hand behind it he's never worrying Bob. One sided decision with Hill in a bit of a shell or Bob might even catch him at some point.
Foster. Virgil would try to use his footspeed advantage but Bob would walk him down. If Hill stops moving and tries to outbox Bob from the outside, Bob has the height and reach to hit him without Hill reaching him. And no way Hill can hurt Bob. Hill was very resilent himself, so I don't see a KO either way. Foster by UD
Are the paramedics nearby when this fight happens? Marie Antoinette had a better chance against the guillotine as Hill does against Foster.