How much power/go-go did I leave on the table?

I replaced the log type exhaust manifolds, and they are still on there. I read something about new/rebuilt engines ruining header finishes during break-in and tuning

I am running the Ebrock 2176 dual plane, stated power band idle to 5500

Carb is the Ebrock 1404 550 cfm manual choke.

Transmission A727, torque converter and rear end are all stock (I have not messed with any of those)

I dont have exact rear end ratio on hand to reply with.