What intake manifold are you using? Is it a single plane type?
A 500 cfm carb on a dual plane intake is a excellent setup for a stock to moderate 283 build. HOWEVER, the carb may require metering rod and/or jet size changes for best results.
It is also important to heed the wisdom shared by others in this post.ie fuel pump pressure, float setting and timing (also using the correct carb port for distributor advance.
I recommend working with what you have instead of a 2 barrel setup.
