I know on the RB block the Holley Street Dominator is a very good intake. In fact it is know to have very good low end for a single plane. My son runs a Perfromer RPM on the 400 in his Dart and I run the Holley SD intake. My 63 has 60 ft better then his Dart has and the builds are very close as we run the same cam and converter. The Holley SD is the best single plane intake for low end from what I have seen. Ron