What cam do you have in your magnum?
I wouldn't worry about the carb it's fine.
When you get it up and running install a vacuum gauge if pulls too much vacuum on a full throttle run then worry about it.
I got 380hp create engine said to dyno over 400hp. Cam is like 288/296 and .510 ish lift at 108. Carb is a 800 edlebrock.
Car is a little lazy under 2000 rpm and the 2.96 gears doesn't help the situation. Have to drive in 2nd through town until about 40 mph.