A stock intake manifold can be used. But how much flow does it actually leave on the table?

I tested a 906 head flowing 321 cfm @ .700" lift. Here is what happened.

Test (1), ported 906 by itself
Test (2), ported 906, 1968-69 383 manifold 2806301, port matched and mildly plenum blended & 4401S AVS
Test (3), ported 906, box stock 383 Victor intake, 4401S AVS


Lift........(1)...........(2)...........(3)

.100........71............69............69
.200.......150...........131...........143
.300.......209...........172...........203
.400.......257...........187...........234
.500.......292...........199...........259
.600.......313...........203...........273
.700.......321...........204...........273

With a good intake manifold you can get the same flow at .300" lift as you can with a port matched and plenum blended stock manifold at .600" and .700" lift. Start changing carburetors and the flows increase even more.