If you do introduce these two dogs you need to do it in a highly controlled way. It needs to be on neutral ground where the pit bull does not feel he needs to defend his territory. Both dogs must be on a leash and you need to be able to seperate them quickly if aggression is shown. Try not to show apprehension as the dogs will pick this up from you. Slower is better in this case of introductions. Never leave the two of them unsupervised.