Lynn,

With this last system, using a scavenge pump to a remote tank and if the tank was higher than the stock pump - could you run a gravity fed line to the stock pump and what would be the best plumbing set-up?The feed to the pump is gravety feed and a large diameter hose is needed to keep drag to a minimum. At least an inch for short runs. I use 1 1/4" for mine. For feeding the stock pump I would make up a fitting as in the second set of drawings. With two gaskets and holes right through the flat plate oil pan.

 

Do these scavenge pumps run dry periodically and if so does it cause any damage to the pump or are they designed for this? I'm guessing their low pressure pumps and there's not a lot of stress on them.

Generally all three of the pump elements are the same material and the same size. You can order different sizes. I use a 7/8 or 1 inch pressure section and 2 3/4" scavenge sections. All are powdwered  metal. You can get the pressure section in a heat treated form if you like that. When hooked to the pan there is never a dry period for these sections. But there is a lot of air. Air flows from the oil storage tank to the engine through the breather hose. The air and oil from the engine mix in the pump and are forced back into the storage tank. The crank case is always running in a slight vacuum. A small air filter on the tank breather is required.