Does it have heat under the intake since there is no heat riser valve? Without a heated intake, it will run really bad till it gets enough heat in the intake to vaporize fuel. I went down that road running three carbs on a home made intake, it took a long time for a mild steel intake to heat up and run right.
The carb spacer is a good idea, it will spread the oil vapors to all six cylinders instead of just the center ones. Drilling the intake and threading would be easy also, it only takes a few threads and some loc-tite to hold the fitting.
