True. In a case between the 3 basic type of spacers, a lot depends on what the engine wants. Generally speaking one could point to this type of spacer on that type of manifold and be correct most of the time but not all of the time. It truly is a trial and error thing.
Running a dual plane seems to like a open or tapered spacer best. That doesn’t mean a 4 hole would not be advantageous. How thick a spacer needs to be, to be a good to a great addition is also a trial and error issue. More is t always better. This whole thing is very combination dependent.
The problem behind this whole discussion is the serious lack of room under the hood. A drop base is already needed and a spacer just kills the deal.
The choice is a spacer under the carb and choke off air flow or no spacer and get as much air flow into the carb as possible. Which is a space (above the carb) challenge under challenge right now. To get and use the ideal set up will require a hole in the hood.
