Hi, and welcome to Steve's!
I'm putting an LT1 in my Nova, so I know what you're going through. First of all, check the front of your block for a casting number 327 - this will tell you it's a LT1 5.7L. There are other ways to tell, but that's the easiest. You mention that it has steel valve covers, which rules out the LT4 - the LT4 used composite covers to keep noise from the valvetrain quiet.
Going to a carburetor is no problem on a LT1. GM Performance parts sells a carb swap intake, but fuel injection will give you the best horsepower, torque, and fuel mileage. If you're hitting 6500 RPM you're going to want a bigger carb than a 650 CFM Holley, it's too small for high RPM and you'll run lean.
Be sure you find out if you have an LT1 before doing too much shopping!