Carb advice?

I have an Edelbrock 1406 600 cfm carb on my Dart right now. It runs and idles beautifully. It is adjusted very well, but the mixture screws are way out. When I floor it it immediately winds up, I start to fishtail, and about when it begins to straighten out it starts to cough and sputter. I am guessing a lean backfire and thinking maybe the carb is too small, or maybe I need to re-jet it. I have no idea what the jets are now, I assume whatever came stock in the carb. I am looking at an Eddy 1413 800 cfm because I like my set up and it will bolt right in with all the same linkages. I am looking for advice, even though I can already sense the can opening and the worms sneaking out ... :-)

73 Dart Sport
318
Edelbrock RPM air gap intake
Edelbrock 1406 600 cfm carb
Comp Cams XE268H cam and lifters
Hooker competition headers with 2 1/2" exhaust
Stock 904 with 2800 stall
Dana 60 with 4.10