What I started to post earlier but then deleted was that is sounds like you have a pretty good motor and rear axle gear combination right now. It might be best at this time to simply work with what you have. Maybe a torque convertor with a slightly higher stall speed to eliminate that lunging when the trans is put into gear. But with your trans in the condition it's in, you might have to put that of until later as well. Your current cam should work fine with power brakes. Keep in mind, sometimes if the carb idle is too lean, the idle speed will have be higher than necessary to keep the motor idling while in gear. When you eventually get to the point of tuning again, sometimes adjusting the A/F mixture with the trans in gear will help.
I've only known a couple of people with basically stock 4 barrel Cleveland motors and they had the same complaint as you, not much low end power.