318 Cam

This is somewhat related to an earlier post about getting 275 horses for a 318. If i have a Comp260 cam in my 318 with manifolds, can i expect an appreciablr gain if i switch up to a Comp XE268? If so, about how much?

Also, would 245-265 horsepower sound like a good estimate for my current combo: 88,000 mile 318 w/ A/C, Edelbrock 600cfm, Performer intake, double roller chain, Comp lifters and springs, new valve seals, comp 260 cam, manifolds, flowmaster 2.5" dual exhaust.

Also, can my stock converter hold up and perform well with the current cam or a XE268?