Looking at the changes you want to make the only things that would alter it from being all original is the soldering would be disturbed which isn’t a big deal, definitely keep the parts, especially the pickups, pots and screws etc and bag them in your case or somewhere safe , you can refit them or include them if ever you wanted to sell it, just my opinion but it’s worth spending a bit more on a nice tort guard, it makes a big difference , good luck and it’s a lovely 78