Valvetrain complete, but a few ???'s

It is syphoning back like syphoning gas out of a gas tank. It will pull the oil right out of the filter if it is allowed to. Amsoil like 99% of the other synthetic oils are the best oils you can use. If you are using a good quality oil and you motor is sealed tight and are using good filtering breathers you don't need that much filter. As for the oil cooler unless you are in a road racing or building a lot heat in your motor you don't need it either. Besides we both know that synthetic oils can handle a much higher level of heat than petroleum based oils can. Warm/hot oils as long as they have not broken down from the heat lubricate better than cool/cold oils. Warm/hot oils also flow thru filters better. But if you are adament that you need this setup what you need is a pressure bypass in the pressure line from the block that will send oil to the motor first then at a given pressure will send the oil to the filters and cooler. Eventually all of the oil will pass thru the filters so it will clean your oil just fine.