It would be rather similar to their actual fight, except that the knuckles would be a tad more vulnerable. Fitz is the better infighter, and much would hinge on how well each adapted to wrestling. Corbett may have a slightly better chance (cuts), but I'd still go with Fitzy here.
If Corbett can get a draw with Jackson under London prize (with gloves) then he can beat Fitzsimmons... Corbett KO40
On the other hand, Corbett is going to get much longer to recover if he's knocked down, and a better start-stop rhythm. He will also be able to drop when tired or hurt. Still, Fitz's energy conserving style will be an issue here.