"Good idea regarding the U shape piping - however my pump instructions specifically call for all pipe to be downward sloping. Are you saying I should have both the source and outlet pipes a little higher than pump height or just the souce?"
I don't know why a pump would need downwards piping? That's just asking for an airbubble to be located right at the pump that way! There may be a reason for it? I don't know that much about pumps really but I know what's worked for me very well for various uses and pumps.
With the pipes going upwards on each side of the pump then the pump should always be full of water. Even if the source goes dry (like pumping from a tank) the outlet pipe stays mostly full while the pump tries to pump air. When the pump shuts off then that water in the pipe flows back into the pump as any air rises to the top. Depending on the pump, most will let the water seep back through, since water seeks it's own level then with the pump not running the water in the outlet pipe should seep back through into the inlet pipe. So if you have say a 2' rise on both pipes and pump dry, after shut down the water should flow back from the oulet pipe and both pipes be 1' full and the pump still be primed.
Many of the above ground pumps have a AC motor that is easily removed, the pump is basically a seperate unit. With such a pump you could install a DC motor various ways.
If you find a motor with the correct mounting and shaft size great and easy. If not, you could make up like a jack shaft of the correct size ( original motor shaft size)and use a sprocket and chain or belt and pulley. Drive the shaft with any motor you want, AC or DC.
You can get fairly cheap 1/2hp 24V dc PM brush type motors. You might be able to find 12V motors, or you could modify a car starter or 2 if you wanted. I would do 2 or 3 at once so I had spares on hand.
Depending on your water needs a 12V car starter would certainly pump water, it would need modded to remove heat for the longer run times, and also need to mod it for a drive system of belt or chain, unless you found a nice gear to match up with it.
Just a few thoughts and ideas.
If I had a shallow well I would be doing such things, but mine is 300'deep and I think the water is 100' down, so I have allot more problems than a 40' well has for pumping.