Carb for 408

Get a holley based carb with replaceable bleeds and restrictions, also buy an AFR gauge set up and have at it. You will learn a lot and know how to tune when you are done. All the new carbs have the fancy metering blocks with way to much emulsion in them and run pig rich on a street car OOTB.
Carb Tunning
The other option is pay someone for their knowledge.