If you haven't removed the injector pump
drive spindle, just make a reference mark on the pump mounting flange and front gear
cover. Then make tiny adjustments until the engine
runs smoothly and starts quickly. The pump is indexed to only mount in one position.
If you have removed the drive spindle (or someone before you has), then you must make sure that it is in the correct position before installing the pump. From the manual, it seems a handy person could do this without the timing disc noted in the manual, 360 degrees is 360 degrees everywhere...just follow the instructions in the manual.
To do it properly, I suppose one should have the 18G269 timing gauge and disc, but if you have the drive spindle in the correct place, you should be able to get it close enough by trial and error. As suggested, the authorized dealer should have the position checking tool, and there are probably other mechanics in the area that do too.