I have a 56 with a 57 312 bored 30 over other than that it is stock other than some port work.I am thinking on putting on a new edelbrock carb and would like some input on the cfm that i need .The ones that i am looking at are the #1803 500 cfm and the #1403 500 cfm.Do you think they are enough or should i go to a 650 cfm