[KULTULZ]

Not a dedicated restoration as the electric wiper motor is showing? If not, I would go with a quality single action pump. No need for a vacuum signal for the heater control is needed either?

What About Dual Stage Pumps?

Many cars used dual stage pumps to help operated vacuum-actuated windshield wipers. The chief disadvantage of vacuum wipers was, without the assistance of the pumps, that under engine loads the intake manifold's vacuum went to zero and the wipers stopped momentarily. This problem was "cured" with dual stage pumps.

The fuel section of a dual stage pump functions in the same way as ordinary fuel pumps. However, the rotation of the camshaft eccentric in the vacuum pump also operates the vacuum booster section by actuating the pump arm, which pushes a link and the bellows diaphragm assembly upward, expelling air in the upper chamber through its exhaust valve out into the intake manifold. On the return stroke of the pump arm, the diaphragm spring moves the bellows diaphragm down, producing a suction in the vacuum chamber.

This suction opens the intake valve of the vacuum section and draws air through the inlet pipe from the windshield wipers. When the wipers are not operating, the intake manifold suction (vacuum) holds the diaphragm up against the diaphragm spring pressure so that the diaphragm does not function with every stroke of the pump arm. When the vacuum is greater than the suction produced by the pump, the air flows from the windshield wiper through the inlet valve and vacuum chamber of the pump and out the exhaust valve outlet to the manifold, leaving the vacuum section inoperative.

With high suction in the intake manifold, the operation of the wiper will be the same as if the pump were not installed. When the suction is low, as when the engine is accelerated or operating at high speed, the suction of the pump is greater than that in the manifold and the vacuum section operates the wipers at a constant speed.

SOURCE - https://secondchancegarage.com/public/535.cfm