This is the rigid metal pipe that runs from the side of the engine over to the back right? I'm not sure the best way to get it out with the oil filter flange on. I recently did mine, but most of the stuff like the oil filter flange, etc., was already removed from the engine. I don't know what year your car is, but for my '79 diesel, it was NLA. I was able to get the pipe from a '78. The only significant difference was there was an extra flange on it. I blocked it off with a rubber cap that I got from Checker Auto Parts, and a hose clamp. Good luck.
Not sure if I had to do it but, since car needed oil change, I dropped oil and filter. The pipe slipped right in with extra space---did not have to touch cooler. No more leak. By the way anyone else have a problem with these pipes rusting out? From the looks of it ...it started from outside and worked its way right through. Luckily I the found the hole in my driveway and not in the middle of nowhere. To moderators --- I think this post should be in troubleshooting