Re: parker nitefly hss....pup upgrade ?
Welcome!
That depends on what you want. Vintage SC sound? Hotter modern sounds? Hum cancelling? Stacked? Side-by-side coils?
I am guessing from the wizard's answer, one aspect you want is quiet. I would drop either Classic Stacks, or Vintage Rails in there. It would keep with the theme of the PG and still offer quiet operation.
Really, some good neck options are (in order of vintage to hot), Classic Stack, Vintage Rail, Cool Rail, Lil' 59....all of those would sound great.
For middle, stick with either a Classis Stack middle, or a Vintage Rail.
If you get a Pearly Gates for the Nitefly, order/buy a standard spaced bucker. A tremspaced humbucker will be too wide for the pickguard.