You’re fine with using the same pump on a 6.9 or 7.3
Ih pumps were governed lower but most were tweaked with by their owners so it may not be set at the original 2700 rpms defuel anymore
Any time you loosen the three nuts holding the injection pump to the housing your timing will change. You will need to time off the #1 line, you don’t need to change the lines to do this, the timing adapter on #4 is for a style timing that is rarely used these days. I would either leave the lines alone, or swap on a complete set from a truck. 7.3s will have the adapter on #1, and 6.9s will have no adapters at all.
Internally, the van, truck, ih, 6.9 and 7.3 pumps are basically the same, just the calibrations were slightly different for various setups. It’s not like the p pumps that have different size plungers for different calibrations.