Be wary of using threaded brass or copper into the block with a lot of plumbing hanging off it. I have had brass pipe fracture at the threads near the block from engine vibrations. The threads greatly amplify the stress concentration in the pipe. A rubber hose connection into a nipple would be better.
Guess I will re-plumb with an iron nipple into the block. Going to be tough as the mock-up was done on the engine stand - as was the final installation which was completed before hoisting the engine and trans back into the car. The drain cock line is in a very tight spot and the pipe needs to loop around the header. And I was trying to keep it as close the block as possible as this is a very busy spot in the engine bay.
