Both are stand-up jabbers, but Hearns a little more mobile and skilled. I think it'll be war of jabs most of the time, Hearns throws it more often, but Foster's is a harder one. I don't think it'd be easy for Foster. Ali has a completely different style from Hearns.
Foster by ko naturally bigger and stronger he would enjoy the advantages that allways worked against him when he met the top heavies.
Tommy's only chance i think is to get Foster before Foster gets him, and at 175 the chances sure are slim. Foster may or may not have had the greatest chin, but at 175 i think he's ok here. Tommy can box with anyone but over the duration Foster is going to get someone big in there, and he works the body hard too at times. Terrifying power has Foster.
Hearns puts up a great resistance and hangs in there (with the fight fairly close on points) only to get stopped somewhere near the final stretch of rounds. Tommy's best chance is to KO Foster early, but it's difficult to see this materialising gven Foster's fighting at his very best (more natural) weight and has a solid enough chin. Foster TKO11 Hearns, over the course of 15 rounds.
Foster by a clean ko in either 4 or 5. No one without a reliable chin survives Foster at 175 and Hearns' one Achilles Heel was his lack of a dependable chin. If Hagler was able to ko him just consider what Foster would do to him. Hearns would meet the same fate against Foster as Roy Jones would for that matter.