Can't offer specific help as I've never worked on one of those engines, but most engines have methods, timing marks, etc, to set timing for pump removal/install. But in general terms, most engines time on #1 TDC, I have seen rare exceptions however, might be best to contact a NH service dept and ask them if they'll fax you some specific information, just to be safe about it. Most service depts will willingly offer this info.
At the very least, if you can verify it times on #1 TDC, and if you don't get any info on how to get it there, what I do is bump the starter to verify which direction engine rotates, disconnect the battery, then remove the injectors (gotta disconnect the lines anyway to remove pump, and it makes it easier to bar engine over). Then find a way to bar engine over by hand while holding your thumb over #1 injector hole. When #1 piston begins to come up on compression stroke the pressure will push against your thumb. Straighten a piece of soft tie wire, drop it in the injector hole until it sits on top of piston. Begin to slowly bar engine, the piston will push the wire out of the hole. Stop and adjust position of wire so it doesn't bind as it's being pushed out. When you get to TDC, it will stop pushing wire out of injector hole. You might want to put a mark on crank pulley when you hit this spot, bar engine back, then bar up to TDC again while checking the mark you made just to verify, you're gonna be real close at that point and can begin pump removal.
That's about as far as I can take you. After you've got your spot, it's a matter of removing supply and injection lines, disconnecting line to aneroid valve, disconnecting electrical, might even have to remove that fuel filter as it might get in the way of pump removal. There should be a cover on flywheel end of engine to remove and access pump drive gear. I have know idea what's going to be required there, typically a nut on shaft to remove, but I can't tell what that small gear in illustration is and what it does. Most injection pumps have a tapered shaft, which requires a puller to pull gear from pump shaft, but again, I can't tell how that one is set up.
Once you get the drive gear sorted out, it's time to remove mounting nuts for pump. But before you do that, take a center punch and make marks on nose of pump and plate on flywheel housing where pump mounts, this is to make sure pump is re-installed in the same position before it was removed.
