the main cause for oil pump fractures is due to solid motor mounts . [ you are using solids yes?] as far as the pick up tube goes, a thin wall tube would be much better and easier to support . I would braze a thin wall pickup to the pump and scrap the heavy wall pipe pictured . install the pump and the correct pickup so the pickup is slightly " above " the pan height , then with a 1/4" shim placed completely across the screen section of the pickup ,place the pan onto the engine and bolt it down . now remove the pan and braze the pickup and your clearance is set exactly where you want it. .............from one circle track racer to another !!