ive already purchased the rockers and heads so theres no turning back on them . The heads and rockers were second hand and had done about 1000 miles and were set up with a solid roller prior to me buying them .The engine builder has measured up the lift etc and says the springs had already been changed and are good to go with my cam.The main thing by the sound is the inlet manifold . I might just buy a single plane M1 and when he is running the engine on the dyno , run it with both and see what the difference is and sell the other.
The reason i went with a dual plane was because of this
Edelbrock Intake Manifold Dyno Test :: Single Vs Dual + Air-Gap Vs Regular - YouTube
ben