Recommended 4bbl carb for stock 318

Reality is there is more going on and so there no guarentees. An engine is not a continuous flow device. Different combinations will like different things at different throttle openings and rpms. When there is black residue up into the intake and onto the throttle blades that's pretty good evidence of the pulses and also the flow reversals that can and do occur most noticibly at the lower rpms.

Adapter plates can be problematic because they are thin. This is seperate from whether the discontinuities will effect flow characteristics or droplets shearing etc. Its a question of whether the bearing surface will stay stay sufficiently flat to have decent clamping on the gaskets. Using a stamped plate with an intake with big gap between the sealing surface and the bolts, like the stocker pictured in this thread, is more likely to have have trouble sealing.