There's the small problem of the oil filter outline in one corner. Now I've had time to drive it there are some intersting comparisons with the old engine. The old engine was clapped out but I thought it ran OK, now I have one which is pretty much new it really shows what is different:
Much quieter, what I assumed was diesel knock was the bottom end and pistons, I just thought "well Perkins are loud" but the new engine isn't loud.
Runs a lot cooler, so its wasting less fuel, should be more economical
Starts much faster - will start on first swing even with no throttle, the old engine needed a lot of throttle to start
I would now say if your diesel is noisy, hard to start and overheats don't waste time looking for faults, its probably time for a rebuild