383 Wont Idle with new to me 800cfm DP. Idles and runs ok with Edelbrock/AFB

Sounds like you have a vacuum leak to me, look it over good. People that don't like Holley's can't tune them, Keep the Holley and figure out what the problem is. Take a piece of vacuum hose and stick it in your ear and take the other end and go around the base and if there is leak you will hear it. The power valve is probably open at idle so figure out what you have and change it to what you need.