Dyno Time!
the Ld 340 is a great manifold ,I use to grind the center down another 1/2 inch and gain top end with no loss at the bottom. You need a stouter engine and cam to run the single plane but the ones ive used on chevy 7513s for pro street cars has the best powerband and you would need more converter to run a single plane,minimum 3500 stall