i'm under the impression that he has a truck 390. not a car 390. i've been racing and building fe ford for over 40 years along with the y-block fords. i did most of my racing on the street and a little on the tracks which i've held several track records.i only usen 410's.406's and 428s. 427s are the best fe but you pay through the nose for them.puting a 2x4 intake on a stock engine is just a little to much. a good alum.intake(offy dual port or equaflow 360 with a 600 cfm carb is the best way to go.)anytime you use more than one carb. you better have engine that can walk the walk.the 429 and 460 are so much better than the fe and cid is off the chart i have a 494 in my 69 gaxalie and there is a guy that has a 814cid.i think you will regret putting a 2x4 on a stock 390.don't waste you timme and money my advice.