If you plan to rebuild the engine, I wouldn't recommend using a used pump. As far as what to purchase, that is nearly impossible for me to determine without the engine in front of me. When you do this, you need to take things apart, check to make sure they are not worn beyond specification, if the cylinder bores aren't beyond specification if the crankshaft journals are not worn too far, cam bearings, and the list goes on.
Normally, I have the overhaul procedures, but the 318 isn't offered in the US, so I don't.
If you could find a good, low mileage used engine, chances are it would be less expensive to repair the vehicle. When you overhaul one with this many miles, it can get expensive very quickly.
I hope this makes sense.
Let me know if you have other questions.
Monday, May 30th, 2022 AT 6:34 PM