How much horsepower should I expect?

Thank you for all of your responses.

I did forget to mention this will be a street and a seldom strip car its going into.
It will have a built A518 auto, 2500 stall with 3.55 gears for now..

For the exhaust; I did have long tube headers with 3" collectors on it before, (and I still have them) but I am tired of getting a flattened pipe at the bottom... with the car at normal(or above) height with 215 70R 15s all around.. (I'm changing the rims out for stock rallye's and normal size BF goodrich tires, so it might be a tad lower than before..)What else are my options for exhaust as far as headers and ground clearance issues go? And do I lose horsepower for using the super 40's vs. anything else? Is having 2.5" pipe hurting me over using 3"? I have a set of electric exhaust cutouts on the way too if that would help my exhaust flow problem any..

For the Carburetor: As far as that goes, could I really street it with a holley 950? And is the 750 really too small? any more specific carbs to look up for my application? Would the same size holley carb make make more hp's than the edelbrock I have? (It has been jetted up 1 or maybe 2 steps from what it came off of before if i'm not mistaken)

Cam: with the trans having the 2500 stall, would it be pushing it to put the 274 solid roller in there? comp calls for 2800 stall for that cam...

Heads: If I did have a street port additionally done to the heads, how much more HPs would I expect from that?

Rods: Are the SIR rods bad for 450-500hp? (max rpm: around 6500)