I have a 289 with a Edelbrock 650 4 barrel, Edelbrock Intake, with long tube headers. I have no idea what the internals (cam, etc...) are like. Just wondering what kind of horsepower I might be getting........ thanks

 

200 @ wheels

 

Really depends on what else you've got going on in there. A stock 289 with a 4 bl carb is rated at 225hp at the flywheel. With all the right stuff yours may be over 300hp, but with just what you described, likely around 250.
P.S. If there are no other mods your engine is over carburated with a 650, you may get a better boost with a 600cfm.