If you are building a racetrack only engine why is the compression so low. The 383 rotating assembly I see is for a 1986-up Chevy street engine. They don't give you the flow rate of the heads you have listed. If I was building a cheap 383 engine I would at least buy big enough heads for it to breath. Like these SBC Chevy Aluminum Heads Assembled 210cc 2.02 Angle - KMJ Performance
. Since you have a cast crank I wouldn't spin it any more than 6000 rpm. The wimpy hyd. flat tappet cam is about correct for it. You might be in the 400 hp range. Bump the compression up to 11.0-11.5 and get a Comp Cams XR300HR 12-444-8. .562/.580 lift and 248/254 duration. 110 LSA and 106 ICL. Super Victor Intake and a 850 cfm carburetor. This will at least get you up to 450-480 hp and 482 lbs. of torque Then you will need a 3000 lb car with a 3500-4000 stall and some gears.