It sounds lean though the cfm rating is not the problem but is a easy fix since with bigger carburetors comes the more radical metering blocks and such.
In nascar they sometimes run 390 cfm mech carbs and make 750+hp
If you give everyone here the carb modle# cfm, jetting, power valve/s it will help us improve the quality of advice you'll receive.
If it's a 750 dbl pumper try 73 primary and 80-82 secondary with matched power valve in front, plugged rear pv.
If you are running 2 pv's then square up the jets front and back, make them the same, and pv's should be the same as each other when running 2.
Sounds like lean jetting though.