Rick which P38?
You know there are small air systems out there if it's one of the smaller Lightnings, only need one servo total to operate all three retracts. Air up and spring down, so if there is a malfunciton the gear automaticly drops. I've used the GP10's retrofitted to air in my PZ Mustang, and some other small units from SouthEast models in my 52" P38.
Oh one other thing, nose gear takes a pounding unless you fly off pavement, make sure it beefed up enough to handle it.