Holley makes a street avenger manifold that is a dual plane. they also make the pro dominator tunnel ram manifold . I couldn't find a street dominator?I personally like the Edelbrock line of Dual-plane manifolds. Performer idle-5500, Performer R.P.M. 1500-6500 or the Performer R.P.M. Air Gap 1500-6500+ R.P.M.'s . A Holley 600 vac. sec. is my choice for a small-block chevy . They seem to have so much power right off idle!