Foster will counter Tarver's straight left with his left hook; that was the old school way to fight a southpaw. I think that at some point in the 4th or 5th round, Foster will time him and end the fight. Tarver would be at a disadvantage strategically in that, in his time, the right hand is the weapon of choice against a southpaw. As he moves to line up his left, Tarver would be setting up Foster's hook.
Hmmmm...I lean towards Foster, but not as emphatically as some are. Maybe I am thinking about Foster stopping Finnegan in 14. I admit to not knowing how many other southpaws Foster fought but I think Tarver would give a respectable performance. Foster by decision over 12
Foster gets a decision unless Tarver brutally counters him with a left hand. Both had power. One was chinny and the other didn't throw enough punches. And Foster's record against top fighters of Tarver's size is terrible.
I'm with @PhillyPhan69 on this one. Foster was a monster for sure, but Tarver is being undersold here. The guy fought at heavyweight whilst virtually ancient and still hasn't been stopped, Foster proved he can't replicate HW results. The styles are also something that I think you should look closer at, Tarver was rarely caught clean with the left hook, and wasn't often in right place to be hit with it. Tarver froze up in the first Jones fight, and refuses to throw much whilst in the centre of the ring, which whilst wouldn't give Bob many opportunities, it would let Foster tee off with his jab and take a wide(11-4ish) decision.