Crankcase Ventilation Separators

Positive Crankcase Ventilation before 1963 was through a draft tube.

The following year a separator to remove the engine oil and return the blow-by gases back into the engine via a PCV valve.

Between 1964-1967, there are two types of separators and matching fuel pumps  for the Kent series engines:
1) In/out baffled internal drain separator and AC fuel pump with non-drain tube.
2) In/out baffled separator with external oil drain outlet and AC fuel pump with oil drain tube.

Internal drain separator can be used for either AC fuel pump. Just plug the AC pump drain tube.
External drain separator is only used with an AC pump with a drain tube. Do not plug the separator drain tube when installing a different fuel pump. This will fill the separator with engine oil thus making it dysfunctional.

An excellent explanation on Engine-Breather Systems by Burton: http://www.burtonpower.com/tuning-guides/tuning-guide-pages/engine-breather-system.html

Installing aftermarket  Aluminum Valve Covers.

All gasoline engines need a positive crankcase ventilation ( pressure will find it's way out ) which sucks fresh air through a type of breather system ( vented oil cap, vent tube, or filter attachment on the valve cover )
Most aftermarket aluminum valve covers are sealed with only a small .025 size vent hole on the oil cap. That is not sufficient to allow enough air into the engine. One option would be to drill a hole at the blank rear area of the cover and attach a threaded tube with a small filter.

Aftermarket English Ford Valve Cover