Silly questions:

- Does the distributor engage the oil pump shaft? Arent there a couple of different length shafts?

- Does it pre-oil when you run the pump with the drill?

- Do you get oil in the filter when you turn the engine over? If you do, the problem is downstream of the filter.

- Are all of the proper galley plugs installed?

- Is the pickup submerged in the oil? Wrong pickup length sucks air.