The problem with running 2 dead pots is that the mixture distribution is worse than the stock manifold - the #3-4 cylinders runs richer than the #1-2 and 5-6. This is not an adjustment and can't be "jetted out".
This also holds true for progressive linkage with all 3 working - the center pair is too rich. The cure is surgery inside the manifold, adding a ditch across the runner entrance etc. No, there's no diagram or instructions.
If you run all 3 simultaneous, be prepared for poor response and poor mileage. Use the smallest matched carburetors you can. If you can fit Rochester Model B, the ones used on the early Gen-3 194" L6 are even smaller than the 216" Gen-2.
