Re: 1975 75hp Seal Kit
All the water pump soft parts come in the complete water pump kit, which is the only way to go if your labor is worth anything.
The LU may have one O ring for the shift rod I missed above, but that's it. The water pump and exhaust housing are not considered part of the LU, and the exhaust housing seal is almost always reusable, unless it's beat up during removal.
Generally BRP and OMC before them didn't have complete seal packages as single PN's, only the third party stuff (which I don't use) which often contains stuff from multiple models, which adds some confusion to what's needed.