Interchangeable parts: 6.9 and 7.3

[farmboy17]

Ok so my buddy just acquired an 83 6.9 f250. He turned the pump up and has had it like that for the past few weeks or so... now the truck is running rough only at a certain rpm and we can only come to the conclusion that its the injection pump. Will an IP off a 7.3 fit on a 6.9, ive seen where some people say yes and some no; wanting a clear answer as there pretty much the same motor with different displacement.
Also whats the difference between all of the injectors like the E code, B code, BB code, and turbo'd motor G code i beleive. I know theres more but those are the ones i remember off the top of my head. Does one flow more than the other or something along those lines?
and what other parts can swap from 7.3 to 6.9?

[7.3L F-250]

yes the pumps are interchangable just flow diffrent ccs of fuel